The place I buy gasoline sells 87 and 93 octaine. Been using 93 since I bought my 03 Premium Sport. Since I don't operate my car at WOT I thought that in view of current gasoline prices I'd try mixing half and half, roughly 9 gal.of each. I'm assuming that the result would have been a tank of 90 octaine, but I don't know if octaine shift is proportional to the ratio of volumes of each octaine gasoline in the mixture.
My surprising result was no knock, no decrease in acceleration, and a slight improvement (about 2mpg over the same course) in gas mileage.
I know that higher octaine actually burns slower therfore less knock, than lower octaine. But, a Mustang guy told me that lower octaine also burns more efficiently.???? Not sure I can understand that. What I'm puzzeling over is, what accounts for the slightly better fuel economy. So, I was wondering if any of you other Linclon lovers out there have tried burning lower than the RECOMMENDED 91 octaine and what kind of results you had. My results lead me to believe that I reduced my costs with no decrease in performance and got a mileage benefit. Wonder what would happen if I used 89 0r 87 octaine. Your experiences/thoughts would be most welcome. lol, Lincolnlov

The place I buy gasoline sells 87 and 93 octaine. Been using 93 since I bought my 03 Premium Sport. Since I don't operate my car at WOT I thought that in view of current gasoline prices I'd try mixing half and half, roughly 9 gal.of each. I'm assuming that the result would have been a tank of 90 octaine, but I don't know if octaine shift is proportional to the ratio of volumes of each octaine gasoline in the mixture.
My surprising result was no knock, no decrease in acceleration, and a slight improvement (about 2mpg over the same course) in gas mileage.
I know that higher octaine actually burns slower therfore less knock, than lower octaine. But, a Mustang guy told me that lower octaine also burns more efficiently.???? Not sure I can understand that. What I'm puzzeling over is, what accounts for the slightly better fuel economy. So, I was wondering if any of you other Linclon lovers out there have tried burning lower than the RECOMMENDED 91 octaine and what kind of results you had. My results lead me to believe that I reduced my costs with no decrease in performance and got a mileage benefit. Wonder what would happen if I used 89 0r 87 octaine. Your experiences/thoughts would be most welcome. lol, Lincolnlov


for the $0.75 you would save, its not worth it. several people have had bad results. use whats recommended. dont risk it... its definitely not worth it. if it saved you $20.00 on a fill up, i would be using lower too! but what does it REALLY save you... a dollar or 2 at most???? dont do it!! you may not have bad immediate results, but it will catch up to you eventually. take care of your car. :L

for the $0.75 you would save, its not worth it. several people have had bad results. use whats recommended. dont risk it... its definitely not worth it. if it saved you $20.00 on a fill up, i would be using lower too! but what does it REALLY save you... a dollar or 2 at most???? dont do it!! you may not have bad immediate results, but it will catch up to you eventually. take care of your car. :L

:I High compression+low octane fuel = bad news...if not sooner than later...The octane rating of gasoline tells you how much the fuel can be compressed before it spontaneously ignites. When gas ignites by compression rather than because of the spark from the spark plug, it causes knocking in the engine. Knocking can damage an engine, so it is not something you want to have happening. Lower-octane gas (like "regular" 87-octane gasoline) can handle the least amount of compression before igniting.

The compression ratio of your engine determines the octane rating of the gas you must use in the car. One way to increase the horsepower of an engine of a given displacement is to increase its compression ratio. So a "high-performance engine" (ie 3.9L V8) has a higher compression ratio and requires higher-octane fuel. The advantage of a high compression ratio is that it gives your engine a higher horsepower rating for a given engine weight -- that is what makes the engine "high performance." The disadvantage is that the gasoline for your engine costs more.

The name "octane" comes from the following fact: When you take crude oil and "crack" it in a refinery, you end up getting hydrocarbon chains of different lengths. These different chain lengths can then be separated from each other and blended to form different fuels. For example, you may have heard of methane, propane and butane. All three of them are hydrocarbons. Methane has just a single carbon atom. Propane has three carbon atoms chained together. Butane has four carbon atoms chained together. Pentane has five, hexane has six, heptane has seven and octane has eight carbons chained together.

It turns out that heptane handles compression very poorly. Compress it just a little and it ignites spontaneously. Octane handles compression very well -- you can compress it a lot and nothing happens. Eighty-seven-octane gasoline is gasoline that contains 87-percent octane and 13-percent heptane (or some other combination of fuels that has the same performance of the 87/13 combination of octane/heptane). It spontaneously ignites at a given compression level, and can only be used in engines that do not exceed that compression ratio.

Oops...almost forgot to credit that little gem to www.howstuffworks.com ...like I'm that smart...

Octane improvers are essentially a flame retardant. Low octane gas pings, knocks or detonates because it is easier to ignite. Higher octane is harder to ignite so it doesn't knock because the fuel air mix doesn't burn as easily or quickly. This is very simplified(and probably inaccurate in absolute technical detail) I am sure, but based upon reading about how it works since the 70s and even reading pre WWII Popolar Mechanics. The following is my interpretation of all that I have read on this.

Anyway, from some articles in Car and Driver back around 1990 or so, and some other mags more recently, a gasoline that is just on the verge or very lightly pinging is getting the most out of the gas. This ping threshold can be varied by either octane or ignition advance in most cases. Most modern engines have knock sensors and the computer will advance the timing to this threshold for best mileage and performance. So if you use higher octane the engine can advance more and probably will get good mileage. But there is a limit to how far the computer will go. If you lower the octane the fuel will burn slightly sooner and quicker which may give better mileage, but you might also start pinging which will cause the computer to retard the ignition which will stop the pinging but also loose mileage and performance.

There is a fine balancing act on ping. With lower octane you can but not always get better mileage, but you risk ping. With higher octane you have less risk of ping and you may or may not get as good mileage but usualy better performance.

What was recommended is that if your engine gently pings, ie barely audible and only under load(heat, hill, air density, etc), then you are probably getting the most from your gas. You might loose performance potential since when you romp on it, there won't be as much margin for ping when the computer tries to advance the ignition.

Knock and Detonation are very different from ping and should be avoided at all costs.
They are all different degrees of the same thing, essentially preignition of the fuel before the proper moment. Ping kind of sounds like that, and is usually one of thoses noises you are not sure you are hearing unless you are listening hard and there is no other noise. Knock is the classic loud knocking we hear every once in awhile on radio commercials and such, or like the bad old days when you engine might continue trying to run when you turned it off. Detonation is lmsot like a loud banging or explosion, because it is.

Ping is generally not harmful to an engine in good condition. It is essentially the sound of the fuel just igniting a tiny bit early and pinging the piston.

Knock will harm the engine over time. It the the sound of the early ignition of the fuel hitting the pistons which hammer the rods and bearings.

Detonation is very disticntive and loud and will destroy and engine in short order. It is the fuel exploding and hammering the pistons, rods, and bearings. It will often burn or hammer a hole thru the piston.

Today's modern engines will do their best to control preignition. For better performance we should use premium. For everyday use we can probably get away with 89 octane. For el cheapo grandma driving you could probably get by with 87. My 2004 LS runs OK on 87, with light ping on long hills in warm weather, but it will stumble and cut out if I romp on it. With 91 it runs great when I romp on it. I have not owned mine long enough to see if there is a mileage difference.

Your best tip is to listen to your engine talk to you and feel how it performs. Some of us can get by on lower octane, some of us will need 91+.

Just my interpretation,

Jim Henderson

Come on people if you cant afford 93 octane then you need to sell your LS and buy a Focus. My father always said, "Its nice to own a expensieve car but you better be ready for the fill-ups and repair bills and if you cant afford anything but the payment, then you shouldnt buy the car!" Stick with 93 thats my outlook!

-Scott-

Come on people if you cant afford 93 octane then you need to sell your LS and buy a Focus. My father always said, "Its nice to own a expensieve car but you better be ready for the fill-ups and repair bills and if you cant afford anything but the payment, then you shouldnt buy the car!" Stick with 93 thats my outlook!

-Scott-

:I

Octane improvers are essentially a flame retardant. Low octane gas pings, knocks or detonates because it is easier to ignite. Higher octane is harder to ignite so it doesn't knock because the fuel air mix doesn't burn as easily or quickly. This is very simplified(and probably inaccurate in absolute technical detail) I am sure, but based upon reading about how it works since the 70s and even reading pre WWII Popolar Mechanics. The following is my interpretation of all that I have read on this.

Anyway, from some articles in Car and Driver back around 1990 or so, and some other mags more recently, a gasoline that is just on the verge or very lightly pinging is getting the most out of the gas. This ping threshold can be varied by either octane or ignition advance in most cases. Most modern engines have knock sensors and the computer will advance the timing to this threshold for best mileage and performance. So if you use higher octane the engine can advance more and probably will get good mileage. But there is a limit to how far the computer will go. If you lower the octane the fuel will burn slightly sooner and quicker which may give better mileage, but you might also start pinging which will cause the computer to retard the ignition which will stop the pinging but also loose mileage and performance.

There is a fine balancing act on ping. With lower octane you can but not always get better mileage, but you risk ping. With higher octane you have less risk of ping and you may or may not get as good mileage but usualy better performance.

What was recommended is that if your engine gently pings, ie barely audible and only under load(heat, hill, air density, etc), then you are probably getting the most from your gas. You might loose performance potential since when you romp on it, there won't be as much margin for ping when the computer tries to advance the ignition.

Knock and Detonation are very different from ping and should be avoided at all costs.
They are all different degrees of the same thing, essentially preignition of the fuel before the proper moment. Ping kind of sounds like that, and is usually one of thoses noises you are not sure you are hearing unless you are listening hard and there is no other noise. Knock is the classic loud knocking we hear every once in awhile on radio commercials and such, or like the bad old days when you engine might continue trying to run when you turned it off. Detonation is lmsot like a loud banging or explosion, because it is.

Ping is generally not harmful to an engine in good condition. It is essentially the sound of the fuel just igniting a tiny bit early and pinging the piston.

Knock will harm the engine over time. It the the sound of the early ignition of the fuel hitting the pistons which hammer the rods and bearings.

Detonation is very disticntive and loud and will destroy and engine in short order. It is the fuel exploding and hammering the pistons, rods, and bearings. It will often burn or hammer a hole thru the piston.

Today's modern engines will do their best to control preignition. For better performance we should use premium. For everyday use we can probably get away with 89 octane. For el cheapo grandma driving you could probably get by with 87. My 2004 LS runs OK on 87, with light ping on long hills in warm weather, but it will stumble and cut out if I romp on it. With 91 it runs great when I romp on it. I have not owned mine long enough to see if there is a mileage difference.

Your best tip is to listen to your engine talk to you and feel how it performs. Some of us can get by on lower octane, some of us will need 91+.

Just my interpretation,

Jim Henderson

Jim,

Many thanks. Your remarks seem to square with my experiment.
I too haven't had my LS for very long, just since Jan. So, I've only tried the octaine mixing once. As I said, I think my mixing resulted in 90 octaine and perhaps thats why I didn't get pinging. I was suprised though by the increase in mileage. I think I read on one of these threads, or perhaps it was on another forum that Ford engineers said that 87 would'nt hurt the engine (because of the penta design of the aluminum heads) but would result in less performance and -- less mileage. That's what it says in the owners manual of my wife's Avalon as well. I also note that in the promo material for the new 280hp 3.5L V6 Avalon a footnote indicates that 280hp is only with 91 octain fuel. Hmmmm?
Got to agree with Lickieleo though, the savings of less than $4 on a fill-up isn't much of an incentive to risk engine dammage. Maybe I need to change stations, i.e. buy where they sell 91 octaine cause I sure don't think I need the 93 that I've been using. Nice to hear from you all. Lincolnlov

I've used nothing but 89 octane 10% ethanol blend in my 00...never has pinged

Great write-ups on this!!... The key is the compression ratio... in the 3.9 and 4.6 V8's the ratio range is anywhere from 9+ - 10:1. At that ratio, an 87 Octane fuel will ping and knock... You might save some coin at the pump but will pay for it at the shop!

I always put in the recommended 91+ octane. BTW, Where do you find that? Almost everybody around here in NJ has either 89 or 93. I can't remember ever seeing 91?
I do try to put a container of injector cleaner in once a month or so. That keeps deposit build up to a minimum. I use the Valvoline Synth line. They are infallible!!

gasonline already has "injector cleaner" in it

I've run 87 with 9.8:1 and iron heads, with 15* of initial timing and 35* total...the key is dynamic compression, not static

things such as quench and distance also play a huge role in compression and octane/timing tolerance....take an 9:1 motor with the pistons .01 in the hole and a .05+ quench distance, run it on 93 and see what happens! Bring the pistons out of the hole (in turn increasing compression to say 9.5) with a .04" distance and you can run more timing with less octane than the 9:1 combo could dream of

working with ford engines, I've seen piston to deck range from .015" in to .01" out, and variances of .005 from cylinder to cylinder in some cases...your advertised compression ratio doesn't mean squat when you figure in production tolerances. This doesn't even take into account the chamber volumes which vary 2-3cc on average

I've run 87 with 9.8:1 and iron heads, with 15* of initial timing and 35* total...the key is dynamic compression, not static


I was going to reply with a more crude way of saying this, but I am glad someone gave the true technical version. :)

I also disagree with Grandma getting away with lower octane fuel. If you are climbing a hill at part throttle doing 35, you could get detonation and most people get detonation at part throttle as that is when the computer is usually in it's most aggressive "save on gas" mode. The timing is way up and the mixture is running leaner. Full throttle causes the timing to drop and fuel mixture to enrichen. It's all about driving in the sweet spot of your torque curve and not bogging the engine too much. Slow lazy driving can also cause carbon build-up which will cause detonation also.

I hate spending the extra .20 cents a gallon, but I am used to it as my Mustang is tuned for that as well.

Octane recomendations are just that recommendations. At high altitudes you can get away with lower octane (lower effective compression), at cold temperatures you can use lower octane (lower temps less chance of pre or spontaneous ignition), cruisng down the highway you can use lower octane (light throttle openings).

I've tried 87 octane during the winter (I'm close to sea level) there was a just noticable ping on clutch engagement in first gear from a dead stop. No noticible high speed pinging, which I get on my unmodified Mustang 5.0 (high RPM only) during the summer with the reccomended 87 octane.

As to the savings using 87 year round would save me $200 per year. Winter only would save me $100 (I drive much more in the winter).

So most of the time I use the premium once in Blue Moon I'll fill it with regular.

Lincolnlov, for the improved mileage I'd credit your driving technique or the weather. With warmer weather, your car won't stay in warm-up mode as long.

What you did shouldn't be a problem, though. Effectively having 90 octane is only one point below the recommended 91 octane.

Lincolnlov, for the improved mileage I'd credit your driving technique or the weather. With warmer weather, your car won't stay in warm-up mode as long.

What you did shouldn't be a problem, though. Effectively having 90 octane is only one point below the recommended 91 octane.

Dutch,
Thanks. I did measure the fuel economy with the car's computer over the same driving course and I maintained a steady 65 for my point to point test. There was of course the weather difference. It was warmer when I got the better mileage with the lower octaine fuel. That fits well with your comment re the warm-up mode but both times the car had been driven at least half an hour before fill up. So, I'm still puzzled.
Another issue that I had not considered before is whether or not we really get the octaine that is posted. I live a few miles from a "Texaco" tank farm and you see every brand tanker roll in and out of there -- except Sunoco so it makes me wonder if octaine thing is has as much efficacy as the brand thing. Lincolnlov

I wouldnt put Sunoco, Speedway, and or Super America gas in my LS or Jags. For some reason I think Sunoco's 93 is about a 88.5 runs like crap in my XJS. Again if you cant afford the gas bills then why have one? I am not being rude but it really makes no sense to put your LS through it. Also dont start a thread stating your motor is fired and you dont know what to do cause I will be the first to tell you, "See where cheap a*s gas got you!" Good luck best wishes.

-Scott-

I wouldnt put Sunoco, Speedway, and or Super America gas in my LS or Jags. For some reason I think Sunoco's 93 is about a 88.5 runs like crap in my XJS. Again if you cant afford the gas bills then why have one? I am not being rude but it really makes no sense to put your LS through it. Also dont start a thread stating your motor is fired and you dont know what to do cause I will be the first to tell you, "See where cheap a*s gas got you!" Good luck best wishes.

-Scott-

Scott,
Thanks for your advice and good wishes. The stuff I use is Amoco/BP which I also use in my daily driver Mark and my wife's Avalon. Tried higher octaine in the Mark and it makes no difference -- and it still runs like a champ with over 140k on the clock. For me its not an issue of finding the cheapest gasoline. There is plenty of that around at the no-name places. I'm more interested in whether or not I'm getting what I'm paying for when I buy 93 octaine. Given what we all know what happens at dealers (un necessary repairs etc.) I can't help but think that the octaine ratings we pay for might be as real (not) as the brand differences that are advertised. Lincolnlov

Here's the real deal on what the feds say about octane ratings from the Federal Trade Commission ( www.ftc.gov )

And remember... the posted octane rating is the minimum required by law. Your 89 octane gas can be 90,91 etc. but at a minimum it has to be 89...

The Low-Down on High Octane Gasoline

Are you tempted to buy a high octane gasoline for your car because you want to improve its performance? If so, take note: the recommended gasoline for most cars is regular octane. In fact, in most cases, using a higher octane gasoline than your owner's manual recommends offers absolutely no benefit. It won't make your car perform better, go faster, get better mileage or run cleaner. Your best bet: listen to your owner's manual.

The only time you might need to switch to a higher octane level is if your car engine knocks when you use the recommended fuel. This happens to a small percentage of cars.

Unless your engine is knocking, buying higher octane gasoline is a waste of money, too. Premium gas costs 15 to 20 cents per gallon more than regular. That can add up to $100 or more a year in extra costs. Studies indicate that altogether, drivers may be spending hundreds of millions of dollars each year for higher octane gas than they need.

What are octane ratings?

Octane ratings measure a gasoline's ability to resist engine knock, a rattling or pinging sound that results from premature ignition of the compressed fuel-air mixture in one or more cylinders. Most gas stations offer three octane grades: regular (usually 87 octane), mid-grade (usually 89 octane) and premium (usually 92 or 93). The ratings must be posted on bright yellow stickers on each gasoline pump.

What's the right octane level for your car?

Check your owner's manual to determine the right octane level for your car. Regular octane is recommended for most cars. However, some cars with high compression engines, like sports cars and certain luxury cars, need mid-grade or premium gasoline to prevent knock.

How can you tell if you're using the right octane level? Listen to your car's engine. If it doesn't knock when you use the recommended octane, you're using the right grade of gasoline.

Will higher octane gasoline clean your engine better?

As a rule, high octane gasoline does not outperform regular octane in preventing engine deposits from forming, in removing them, or in cleaning your car's engine. In fact, the U.S. Environmental Protection Agency requires that all octane grades of all brands of gasoline contain engine cleaning detergent additives to protect against the build-up of harmful levels of engine deposits during the expected life of your car.

Should you ever switch to a higher octane gasoline?

A few car engines may knock or ping - even if you use the recommended octane. If this happens, try switching to the next highest octane grade. In many cases, switching to the mid-grade or premium-grade gasoline will eliminate the knock. If the knocking or pinging continues after one or two fill-ups, you may need a tune-up or some other repair. After that work is done, go back to the lowest octane grade at which your engine runs without knocking.

Is knocking harmful?

Occasional light knocking or pinging won't harm your engine, and doesn't indicate a need for higher octane. But don't ignore severe knocking. A heavy or persistent knock can lead to engine damage.

Is all "premium" or "regular" gasoline the same?

The octane rating of gasoline marked "premium" or "regular" is not consistent across the country. One state may require a minimum octane rating of 92 for all premium gasoline, while another may allow 90 octane to be called premium. To make sure you know what you're buying, check the octane rating on the yellow sticker on the gas pump instead of relying on the name "premium" or "regular."

For More Information

If you're concerned about the accuracy of an octane label - or if you don't see a yellow octane sticker on a gasoline pump, write: Consumer Response Center, Federal Trade Commission, Washington, DC 20580.

The FTC works for the consumer to prevent fraudulent, deceptive and unfair business practices in the marketplace and to provide information to help consumers spot, stop and avoid them. To file a complaint or to get free information on consumer issues, visit www.ftc.gov or call toll-free, 1-877-FTC-HELP (1-877-382-4357); TTY: 1-866-653-4261. The FTC enters Internet, telemarketing, identity theft and other fraud-related complaints into Consumer Sentinel, a secure, online database available to hundreds of civil and criminal law enforcement agencies in the U.S. and abroad.

Here's the real deal on what the feds say about octane ratings from the Federal Trade Commission ( www.ftc.gov )

And remember... the posted octane rating is the minimum required by law. Your 89 octane gas can be 90,91 etc. but at a minimum it has to be 89...

The Low-Down on High Octane Gasoline

Are you tempted to buy a high octane gasoline for your car because you want to improve its performance? If so, take note: the recommended gasoline for most cars is regular octane. In fact, in most cases, using a higher octane gasoline than your owner's manual recommends offers absolutely no benefit. It won't make your car perform better, go faster, get better mileage or run cleaner. Your best bet: listen to your owner's manual.

The only time you might need to switch to a higher octane level is if your car engine knocks when you use the recommended fuel. This happens to a small percentage of cars.

Unless your engine is knocking, buying higher octane gasoline is a waste of money, too. Premium gas costs 15 to 20 cents per gallon more than regular. That can add up to $100 or more a year in extra costs. Studies indicate that altogether, drivers may be spending hundreds of millions of dollars each year for higher octane gas than they need.

What are octane ratings?

Octane ratings measure a gasoline's ability to resist engine knock, a rattling or pinging sound that results from premature ignition of the compressed fuel-air mixture in one or more cylinders. Most gas stations offer three octane grades: regular (usually 87 octane), mid-grade (usually 89 octane) and premium (usually 92 or 93). The ratings must be posted on bright yellow stickers on each gasoline pump.

What's the right octane level for your car?

Check your owner's manual to determine the right octane level for your car. Regular octane is recommended for most cars. However, some cars with high compression engines, like sports cars and certain luxury cars, need mid-grade or premium gasoline to prevent knock.

How can you tell if you're using the right octane level? Listen to your car's engine. If it doesn't knock when you use the recommended octane, you're using the right grade of gasoline.

Will higher octane gasoline clean your engine better?

As a rule, high octane gasoline does not outperform regular octane in preventing engine deposits from forming, in removing them, or in cleaning your car's engine. In fact, the U.S. Environmental Protection Agency requires that all octane grades of all brands of gasoline contain engine cleaning detergent additives to protect against the build-up of harmful levels of engine deposits during the expected life of your car.

Should you ever switch to a higher octane gasoline?

A few car engines may knock or ping - even if you use the recommended octane. If this happens, try switching to the next highest octane grade. In many cases, switching to the mid-grade or premium-grade gasoline will eliminate the knock. If the knocking or pinging continues after one or two fill-ups, you may need a tune-up or some other repair. After that work is done, go back to the lowest octane grade at which your engine runs without knocking.

Is knocking harmful?

Occasional light knocking or pinging won't harm your engine, and doesn't indicate a need for higher octane. But don't ignore severe knocking. A heavy or persistent knock can lead to engine damage.

Is all "premium" or "regular" gasoline the same?

The octane rating of gasoline marked "premium" or "regular" is not consistent across the country. One state may require a minimum octane rating of 92 for all premium gasoline, while another may allow 90 octane to be called premium. To make sure you know what you're buying, check the octane rating on the yellow sticker on the gas pump instead of relying on the name "premium" or "regular."

For More Information

If you're concerned about the accuracy of an octane label - or if you don't see a yellow octane sticker on a gasoline pump, write: Consumer Response Center, Federal Trade Commission, Washington, DC 20580.

The FTC works for the consumer to prevent fraudulent, deceptive and unfair business practices in the marketplace and to provide information to help consumers spot, stop and avoid them. To file a complaint or to get free information on consumer issues, visit www.ftc.gov or call toll-free, 1-877-FTC-HELP (1-877-382-4357); TTY: 1-866-653-4261. The FTC enters Internet, telemarketing, identity theft and other fraud-related complaints into Consumer Sentinel, a secure, online database available to hundreds of civil and criminal law enforcement agencies in the U.S. and abroad.

Steve,
Thanks for the governmental info.
Having worked for the Feds in the past I am painfully aware that the regulatory capabilities of the responsible agencies leave a lot to be desired. Just as we found after 9-11 with the FBI, CIA etc. Things aren't what they should be.... Infact govt. regulatory agencies rely HEAVILY on industry self policing. Kind of like the fox guarding the hen house. Ever notice that when there is a recall mandated by the govt., whether hamburger or car baby seats, there is usually a consumer group that prodded the feds to make the recall. I suspect that the regulation of octaine follows a similar pattern. I don't want to sound too jaded but wonder if we are being ripped off by the oil companies. Lincolnlov

Steve,
Thanks for the governmental info.
Having worked for the Feds in the past I am painfully aware that the regulatory capabilities of the responsible agencies leave a lot to be desired. Just as we found after 9-11 with the FBI, CIA etc. Things aren't what they should be.... Infact govt. regulatory agencies rely HEAVILY on industry self policing. Kind of like the fox guarding the hen house. Ever notice that when there is a recall mandated by the govt., whether hamburger or car baby seats, there is usually a consumer group that prodded the feds to make the recall. I suspect that the regulation of octaine follows a similar pattern. I don't want to sound too jaded but wonder if we are being ripped off by the oil companies. Lincolnlov

For you performance buffs have a look at this site! Sorry I don't know how to hotlink it. But it seems to explain to me how I got the results that I did from my unscientific test with my 87/93 octane mix. http://www.diabolicalperformance.com/hotrodoctane.html
lincolnlov

Right, but if that were true wouldn't this report tell you that higher octane petrol will give you performance gains? I think the recommendation for use of higher octane fuel to help eliminate knocking or pinging is still there for the few carbeurated engines still being used. Of course...most people still using those types of intakes would hopefully have the knowledge to tune their air/fuel mixture...

So bottom line, after all we've read here. What are you going to use??? I have tried 87 Octane in my LS when I first bought it. My average around town gas mileage was 12-14 MPG. When I was first driving it, I told my wife this car is suppose to have balls, my Continnetal was faster. I then changed to 93 Octane. I noticed the difference after about 2 tanks. Better mileage and more balls. Well I'm going to stick with the 93 Octane. Now even though when I was using the 87 the car did run fine, no ping. And as long as I didn't want the extra nuts it's okay. My Continnetal on the other hand sais Premium RECOMENDED.... Notice the word. It ran no different on 87... We took a trip last year and got a record 29 MPG..Only when my wife drove that is. But the LS does not say RECOMENDED.

Fordman,
The owners manual for my 03 Premium Sport does say "91 octane recomended" So I guess I'm wasting $ buying 93. But, am resistant to change (for no logical reason) so rather than look around for 91 I'll probably stick with 93. Superstition, luck and religion, all defy logic! Lincolnlov

Just beware of the additives with the MTBE in them, they have a nasty tendacy to leave orange-ish deposits in the engine and cats, and it's all that swift for the environment either. Don't get me wrong, I'm no bunny hugger, but the stuff is worse than the gas itself.

I've run straight 89 in mine, with no problems other than launch, then it's a little flat. 89 and 92, no difference in performance. 87 and 89, pings, and I never went any further down. Don't mention this to Quik LS as he will have your head, and remind us that Ford's engineers claim there is not enough trim in the computer to take out enough timing to make this work. I believe they said that to him, but I do not believe it is true. If the car runs and doesn't ping, guess what, there's enough trim there. I wouldn't try to run the car at max performance with less than 91 fuel, but for highway use and general puttering around, personally, I see nothing wrong with it.

What's more interesting is the variations from manufacture to manufacture, right now, Sunoco's 93 seems to be the favorable flavor. It was BP for about 2 months, then I started loosing milage. Here in Western PA, who knows what gas your getting they change it by the season, and what county you buy it in... thanks to the aforementioned bunny huggers that I am not one of...

I've nerver heard of a "bunny hugger".

Thats some funny $hit. :Beer

Just beware of the additives with the MTBE in them, they have a nasty tendacy to leave orange-ish deposits in the engine and cats, and it's all that swift for the environment either. Don't get me wrong, I'm no bunny hugger, but the stuff is worse than the gas itself.

I've run straight 89 in mine, with no problems other than launch, then it's a little flat. 89 and 92, no difference in performance. 87 and 89, pings, and I never went any further down. Don't mention this to Quik LS as he will have your head, and remind us that Ford's engineers claim there is not enough trim in the computer to take out enough timing to make this work. I believe they said that to him, but I do not believe it is true. If the car runs and doesn't ping, guess what, there's enough trim there. I wouldn't try to run the car at max performance with less than 91 fuel, but for highway use and general puttering around, personally, I see nothing wrong with it.

What's more interesting is the variations from manufacture to manufacture, right now, Sunoco's 93 seems to be the favorable flavor. It was BP for about 2 months, then I started loosing milage. Here in Western PA, who knows what gas your getting they change it by the season, and what county you buy it in... thanks to the aforementioned bunny huggers that I am not one of...
Hey Kleetus how yins been duin? Yea, I agree,who knows what we are getting though we may be payng for 91 or 93. Ya know Quick doesn't have to deal with the cold very much so things could be different down there. Sure wish I had access to some Ford Engrs. I got a pile of questions.
The surging I had in Feb. disappeared as soon as LM fixed my transmission with new solenoids and valve body. Gota admit that they did it with a smile and even called this week to see if I am satisfied with the work. The rich fuel smell still occurs on start up.
Around here bunny huggers and tree huggers hold hands so they can do the bunnies and trees at the same time. While I'm no bunny/tree hugger, I can appreciate the effort. If you ever go to East Europe or Russia it quickly becomes evident that there was and still is little regard for the environment --- its pretty sad so see. And, easy to see why they want to "enjoy" vodka so much. Lincolnlov

I'll just say this:

The spark in the tables is set to a pretty conservative setting...I personally wouldn't run under 91 because of the difference in gas milage from retarding the timing....

That said, I run 93.. Yes, the car DOES add in a few degrees (I forget the exact #, but I think for most spots it was another 3 degrees) of advance...

-Matt

I've used nothing but 89 octane 10% ethanol blend in my 00...never has pinged

K N O C K S E N S O R S, no kidding theres no ping. Using lower octane saves so little money over the coarse of a year its ponitless. If the car asks for 91 (premium) then not using it causes a knock sensor equipped car to pull timing. Less power, and usually worse emmissions and mpg as well.

Well, using a lower octane fuel (which ends up being a longer chain molecule) does have an increase of BTU's per volume of gas, which can lead to more power and better fuel economoy, to a point. The difference in energy content between 10% ethonol and preimum (which can contain up to 10% ethonol without having to have it listed, and if you ask for a gasoline breakdown sheet, this will be proved) isn't much more than about a 2% BTU differance. And running the lower octane in an engine with a high compression ratio, it will knock, as detonation is not based on the spark event but instead of the ignition temperature of the fuel. Knock sensors are used to tell the computer when spark timing has been advanced to far, and to pull back timing. Ignition timing really has no effect on detonation. So if you use low grade fuel and your engine is detonating, the computer will see this as overadvanced timing, and pull a few degrees out, this learned spark table may then lead to a decrease in fuel economy, while still not curing the violent detonation.

If it says 92, run 92, its not worth an engine for a few bucks. If you can honestly say you know all there is to know about the fuels/engine, combustion chamber characteristics, air distribution, you could probably figure what you can get away with. But if you don't know those things, just use what the book says.

On the other hand, if there is a supercharger kit for these engines that will still run on premium fuel, that is a pretty convincing argument that a stock engine will run on 87 fuel, as the difference isn't that great, but is still enough.

Now in my turbo 4cyl, I ran 12psi of unintercooled boost down an engine rated at 9.5:1, I did have minor detonation problems, as this was the edge for the gas I was running (92 octane) and chamber design. After pulling the engine back apart this fall, it was obvious another 2psi would have led to an engine failure..... Things to think about when playing with fuels......

Hey Kleetus how yins been duin? Yea, I agree,who knows what we are getting though we may be payng for 91 or 93. Ya know Quick doesn't have to deal with the cold very much so things could be different down there. Sure wish I had access to some Ford Engrs. I got a pile of questions.
The surging I had in Feb. disappeared as soon as LM fixed my transmission with new solenoids and valve body. Gota admit that they did it with a smile and even called this week to see if I am satisfied with the work. The rich fuel smell still occurs on start up.
Around here bunny huggers and tree huggers hold hands so they can do the bunnies and trees at the same time. While I'm no bunny/tree hugger, I can appreciate the effort. If you ever go to East Europe or Russia it quickly becomes evident that there was and still is little regard for the environment --- its pretty sad so see. And, easy to see why they want to "enjoy" vodka so much. Lincolnlov

Oh yeah.. I forgot you were from da burg. In case you forgot about up here, it's construction season... no spring, just lots of orange barrels springing up all over the roads. Without trying to steer this thread to environmental issues, Our Beloved Govn'r Ed Rendell singed us up for all the C.A.R.B. crap that California has to live with... such niceties like statewide emissions testing, no carburetor adjustments on lawnmowers, chainsaws or small engines unless you go to the dealer, or make your own tool to adjust mixture... Oh, and did I mention you can only buy three handed gas cans now? That would be one to hold it up, one to point it into the tank, and one to operate the vapor/child/generally-any-human proof spring loaded valve. You might actually need two hand for that part. I hear you about Eastern Europe, we do a lot of business there because we can't get silicon product made here in the states anymore. That's okay, I'm sure more people won't mind being outsourced to other countries for the sake of our pristine environment that no one can afford to live in.

Sorry... am I rambling?

Kleetus,
Yeah, we've got all those environment saving things here in Va. -- emissions tests, specially formulated gasoline (thats why I wonder what I'm really getting from the pump), no carb adjustments, no open burning, etc. -- except for the silly gas cans. We still have bad air. Its just too many durn people in one place. China has the solution though. They just don't know it. Their air is so bad that in some cities the av. life span is in the 50's and falling. They'll achieve a balance the natural way.
Bet that your gov. doesnt really care too much about clean air but more about the big pile of federal $ that Pa. will get for they implementing more freedom suffocating red tape. Over where my brother lives in the Kiiski Valley them boys know how to deal with the govt. though. They ignore it and basically do as the please -- no feds,no police.
Yins stay good. Lincolnlov

Well, using a lower octane fuel (which ends up being a longer chain molecule) does have an increase of BTU's per volume of gas, which can lead to more power and better fuel economoy, to a point. The difference in energy content between 10% ethonol and preimum (which can contain up to 10% ethonol without having to have it listed, and if you ask for a gasoline breakdown sheet, this will be proved) isn't much more than about a 2% BTU differance. And running the lower octane in an engine with a high compression ratio, it will knock, as detonation is not based on the spark event but instead of the ignition temperature of the fuel. Knock sensors are used to tell the computer when spark timing has been advanced to far, and to pull back timing. Ignition timing really has no effect on detonation. So if you use low grade fuel and your engine is detonating, the computer will see this as overadvanced timing, and pull a few degrees out, this learned spark table may then lead to a decrease in fuel economy, while still not curing the violent detonation.

If it says 92, run 92, its not worth an engine for a few bucks. If you can honestly say you know all there is to know about the fuels/engine, combustion chamber characteristics, air distribution, you could probably figure what you can get away with. But if you don't know those things, just use what the book says.

On the other hand, if there is a supercharger kit for these engines that will still run on premium fuel, that is a pretty convincing argument that a stock engine will run on 87 fuel, as the difference isn't that great, but is still enough.

Now in my turbo 4cyl, I ran 12psi of unintercooled boost down an engine rated at 9.5:1, I did have minor detonation problems, as this was the edge for the gas I was running (92 octane) and chamber design. After pulling the engine back apart this fall, it was obvious another 2psi would have led to an engine failure..... Things to think about when playing with fuels......

Putter,
Think you have been the only one who has clearly touched upon the reason (more Btu's per gal.) that I got better mileage from 87/93 (presumably 90 mix) than I got from straight 93. Just seems that a 2mpg increase is more that I could have expected. Thanks Lincolnlov

What does your fuel filler door say on the back? Mine says 91+. The gummint mandates that ALL cars will run on 87. That doesn't mean that 87 will provide the best efficiency, just that the engine will run. My manual also states that even at high altitude, 91 is still the recommended octane.

For cryin' out loud, you bought a performance, luxury sedan. Don't skimp on something as critical as fuel!!!!

LS4me,
Hear ya. But I think Putter-GLHT came pretty close to answering my original question. i.e. why did I get better mileage, under essentially the same dirving conditions, from 90 octane than I get from 93. Answer, lower octane has more BTU's, equals more energy. I knew that higher octane burned slower but didn't know that it containes fewer BTU's per unit volume. Lincolnlov

I just wanted to add a comment to this. I know nothing about all this gas stuff, but i did just see on the news about two weeks ago in Milwaukee, that a lot of stations in the area are selling 93 but it is really 87. It was an investigative report that one of the news stations did.

It wasnt just one station it was a lot of them, all owned by different people.

Needless to say they are now getting investigated by the state.

Just thought I would ad that you might really never know if you are getting what you pay for. You have to trust the gas station's business practices as well as the gas.

Yep IFORGITED
That is what I was alluding to in the first page of this thread, (are we really getting the 93 octane we pay for) when I mentioned that at a nearby tank farm every brand tanker but Sunoco (cause its blue at the pump) is in and out of there. Can it be that the octane we pay for is just like the brand we pay for? Lincolnlov

K N O C K S E N S O R S, no kidding theres no ping. Using lower octane saves so little money over the coarse of a year its ponitless. If the car asks for 91 (premium) then not using it causes a knock sensor equipped car to pull timing. Less power, and usually worse emmissions and mpg as well.


lower octane with less timing doesn't make less power than higher octane and more timing...the combustion still takes place at the same "time" per crank degrees. You can actually lose power by running too much timing with a higher octane fuel, w/o preignition coming into play. Every engine has a "sweet spot" when it comes to timing, octane, a/f ratio, etc.

As long as your car doesn't reach a point of preignition, it doesn't matter which fuel you run...the power difference (if any) is insignificant

Knocksensors don't trigger any advance to be pulled unless there is knock to begin with...

Hi guys,

I'm glad someone started a thread on this subject. I have a 2000 LSv6 with 61000. I had used the 91 octane from Quicktrip religiously. However, I could hear a noticable pinging when driving in the inside lane next to the median wall. I tried fuel injector cleaner, no help. Thought that maybe it was something with the miles on the car. I couold live with it. (before I would take it in for a tune up) Recently a friend(?), told me that he heard that it was ok to run 89 octane in the car. Boy oh Boy, WRONG!!!!! The pinging got worse! At low speeds on the streets, I thought my car was going to die, I crindged everytime I gave it some gas from a stop sign. After half a tank full, ( and a very bad headache)I went back to Quicktrip, bought the STP fuel injector cleaner, and filled up with 91 oct., I drove a few short miles around the neighborhood over the weekend (I was babying it). I finally had to venture out onto the highway on Sunday . I heard the pinging starting, soooo, I thought the hell with it (do or die), I floored it. Needless to say the pinging is gone, (very very slight if noticable) and the hesitation that I had before is gone, I'm hoping the gas milage improves.
It is if FINALLY I have my perfect car. :Beer :dj:

lower octane with less timing doesn't make less power than higher octane and more timing...the combustion still takes place at the same "time" per crank degrees. You can actually lose power by running too much timing with a higher octane fuel, w/o preignition coming into play. Every engine has a "sweet spot" when it comes to timing, octane, a/f ratio, etc.

As long as your car doesn't reach a point of preignition, it doesn't matter which fuel you run...the power difference (if any) is insignificant

Knocksensors don't trigger any advance to be pulled unless there is knock to begin with...
MAT88GT,
Agree with you completely! In the OLD days the driver had a lever on the column with which he/she could adjust the advance to achieve the sweet spot. And while I'm old, I'm not that old. But there was one and was on atractor that I used to operate. Had to get the spark right to get the max pulling power. Lincolnlov.