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2002 LS V8

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I just purchased a 2002 LS V8 and I don't have the manual with me. Does it need or prefer premium gas? If so what octance gives the best performance?

Thanks
 
2002 LS V8 said:
I just purchased a 2002 LS V8 and I don't have the manual with me. Does it need or prefer premium gas? If so what octance gives the best performance?

Thanks
It states in the owners manual that the LS was designed to use Premium fuel. Here's a snap shot of page 228 in my owners manual:

fuel.jpg
 
It should also give you the octane requirement on the inside of the gas cap cover.
 
I don't yet have enough "experimental" evidence but I am beginning to suspect that octane level affects the mileage on these cars, significantly.

I have been playing with regular, midgrade and premium for the past few months. Most of the time I was running 89 octane since that seemed to be a good compromise what with gas prices etc. The 89 has never caused any ping with my car including a fairly steep hill in 4th on hot days. The 87 does cause some slight pinging on that hill and under hard sudden acceleration I have noticed at least knocking and I think throttle retardation.

I have not noticed any significant differences between 89 and 91 EXCEPT, I think that the 91 does give significantly higher mileage, maybe 1-2 mpg above my average of about 14mpg on my short commute. I also think that the engine "tunes" itself to work with the average gas it sees, and when it suddenly gets higher octane, it takes advantage of the higher octane and advances the ignition resulting in better mileage. Then when you go back to a lower octane the mileage drops below what it used to average with the same gas, hopefully only til the computer "relearns" the timing curve.

As an example. I had been running 89 octane over the past month averaging about 14mpg. I switched to 91 a week back and average something like 16mpg. I put in 89 this weekend and no it looks like I am averaging 12mpg instead of 14mpg as before on the same gas.

I will be experimenting a bit more but this is interesting. Of course my results could just be due to the hot weather we have which would drive down mileage due to AC and more likelihood of pinging coupled with the octane drop and lower air density.

BTW, it is my opinion and a lot of automotive rags, that except for extremes, running a lower or higher octane is not harmful to most modern computer controlled cars. The computer will adjust for a fairly wide range of conditions. As long as your engine is not always pinging or worse knocking, the engine should be fine. However you may not get optimum performance or gas mileage. Mileage versus octane is what I am playing with here.

Just my unscientific opinion, so far,

Jim Henderson
 
Jim...the reason you are seeing better mileage out of the higher octane is indeed detonation! What most people don't understand is higher octane fuels burn SLOWER than lower grade. The combustion process is more controlled and not as violent. It is absolutely true that running higher octane than necessary can indeed HURT mileage due to this. But if your car needs the higher octane to keep it out of detonation, then abosolutely you should run it. Another issue that many don't realize is the computer systems and knock sensors these days are so sophisticated that it will detect detonation long before you can hear it. When that happens, it pulls timing. That is what's happening with your 89 octane. It's not as bad of detonation as you get with the 87 octane, but it's still there and the computer reads it. With the 91 or higher, no detonation at all, so no timing is pulled...and your mileage is better.

This is very easy to see if you have access to a NGS Star tester or other data logging equipment. Just read the amount of knock retard while driving the vehicle. I think you will be amazed at what goes on...and you don't hear a thing. Been there, done that and got the T shirt!!
 
Yes, the computer controlled engines do detect knock and retard ignition accordingly which of course affects performance and mileage if the retard is significant. As the section in the paragraph under the big 91 in the previous posting above says... "Do not be concerned if your engine sometimes knocks lightly..." What that means by my understanding and the car rags is that if it does knock the computer is taking over and preventing any serious knock. If it still knocks then it is definitely time to move up.

There is a pretty wide line between where knocking affects mileage to where it causes damage. You need a pretty consistant knock or hard knock(kind of a rattle) to significantly harm the engine, least according to several articles I have read over the years. First time I became away of this issue was way back when I had an 89 SHO which recommended 91 and Car and Driver had a big article about octane and engine computers etc. I did similar experiments then and found the SHO worked well on 87 to 89 in cooler months and pinged just a big on it during summer months with AC and up this long hill in 5th on my commute. 91 octane eliminated the ping.

What is surprising me so far on this current tank full is that with about 70 miles on the tank I still only register less than 13mpg. Of course I haven't gone on the freeway yet and that significantly affects the mileage average. Should see tonight with my 80 miles of freeway flying.

The LS at least in early indications is more sensitive to gas than any of my previous vehicles except for a 12.5:1 engine I once had, that one was a real octane pig. The SHO seemed somewhat sensitive. My 86 Turbo coupe was somewhat sensitive, my 79 TA didn't seem to care, my 96 SS didn't give a hoot, my other cars were regular gas slurpers.

The LS seems to run OK with 89, MIGHT run better with 91 and pings a bit under hard load with 87, this is very similar to what my SHO did, but so far the mileage may be more affected on the LS.

More experimenting to do. And it is not scientific since I cannot completely control conditions and my bad mileage tank is during very hot weather and no cruise codntions yet. Would love to play with an engine analyzer since I am sure the advance is tweaking back and forth depending on conditions, but that is what the computer is for. Members of the SS group had done similar datalogging and indeed the knock sensors and computer would run up and down the advance curve as required.

Just some thoughts until I finsih playing around. When gas gets to 3 or 4 bucks a gallon, this experimenting will come in handy.

Jim Henderson
 
I am still having Issues with my MPG being completely steady at 17.2 *has been for 2 weeks now* but my til empty gauge goes up and down like crazy... dropped 47miles til empty today on a 5mile drive on the highway... Could there be an issue with my fuel line because it is actually reading correctly as far as I can tell in consistance with the actual fuel gauge, but it's driving me nuts seeing it vary so much. I only run 91 octane, and have since I got the car last october..
 
On the SHO V6. see the following:
http://www.shotimes.com/php-bin/modules.php?op=modload&name=News&file=article&sid=51
The author of the article is (or was, at the time) a research engineer for Ford who also campaigned his SHO in the One Lap of America. (It's also worth noting that the article was written almost ten years ago, so parts of it do not necessarily apply to the LS's engines.) IIRC, the SHO V6 was a relatively low compression engine (around 8.5:1 or 9:1).

I can't vouch for the V6, but the LS's 3.9V8 does require 91 or better; its compression ratio is 10.5:1 ('00-'02) or 10.75:1 ('03 and later), which is fairly high for a street engine. There's also a warning from Ford (I'm not sure if it's TSB) issued in May, 2005, that using gas with an octane rating below 91 in the 3.9l V8 will "cause engine knock concerns, 'pre-detonation', and possible engine damage." The engine controls are calibrated to run on 91 octane, so if you're using a lower grade, you're forcing the PCM to continually compensate for running outside of its normal parameters (ie, it will have to retard timing more frequently and by a larger amount). As a result, you'll see lower performance.

Aside from lowering performance, you're also removing the engine's margin of error; as anyone who's familiar with science and engineering--and computing in particular--can tell you, the boundary conditions are where things tend to go bad in a big way and in a big hurry.

What you do is up to you, but we're talking about a difference of less than $4 per fill-up. If that's a big deal, you need to sell your LS before something breaks, because you won't be able to afford to fix it...
 
Well my theory that octane was significantly affecting mileage may be dying. Got a good 100+ miles of freeway cruise at 70 or so on it yesterday and today. That brought my <13 mpg upto 15+(which is in the ballpark of my mixed commute and freeway average). so now I doubt that the computer is retarding the advance into the toilet which would cause poor mileage. I think the commute is the major factor now in my wide swings in mileage.

I am leaning more and more to the theory that my commute being less than 10 miles one way the engine really doesn't warm up. If all I have is commute miles, the mileage is lousy. As I get more freeway miles the mileage becomes acceptable for mixed driving but short trips. I have not yet had a chance to do a full tank full at freeway speed. I really need to make one of my I5 LA to Portland and back runs with different octane. That should tell quite a bit.

Interesting that my old 96 SS had 10.5 compression and the factory recommended 87 octane and I never, ever had any problems no matter what kind of driving I did. Strange that Ford couldn't do the same with a newer technolgy engine. The LT1 had reverse flow cooling and that was claimed to be a big part of running regular at 10.5 compression, that, along with computer knock control. I am guessing the LS engine is more stressed and high strung and so more sensitive to octane. Oh well apples and oranges.

I do know that 87 will ping under load with the LS and if you punch it, the engine may even stumble, so definitely not adequate fuel for the LS. 89 appears to be about the minimum in my driving "experiments" that doesn't have any audible or "driver feel" symptoms of ping. I am sure the computer is running up and down the advance curve tho, as that is it's job. May have to work harder on 89.

Again THe LS vs SHO vs SS is apples to oranges to watermelon comparison so you really can't read too much into the following... The 89 V6 SHO is what I had and I think it was 10.0 or more compression if I recall correctly. The Car and Driver article( SHO CLUB reprint... http://www.shoclub.com/ goto SHO History) printed in 92(maybe out of date thinking?) essentially said the Ford engineers tested the V6 and...

>>>Some cars benefit from fuel higher in octane than the 87 PON (pump octane number) of regular unleaded. But not many. In fact, one of the most exotic engines on the market today runs happily on regular: the 24-valve V-6 in the Taurus SHO. Above 3600 rpm, it delivers its full output on 87 PON gasoline. Premium and super premium add nothing but gravy for the oil companies.

Ford recommends premium fuel for the SHO V-6( they also Recommend it for the LS, my notes). It’s plainly a high-performance engine, and Ford decided upon premium way back in the concept stage to avoid design constraints on power out put. But when the job was finished, the resulting engine worked fine on regular fuel, primarily because modern engine technology eliminates the bungling operation that, in past engines, could only be smoothed over by high-octane fuel.... If your engine doesn't ping on regular, premium will do nothing for you. Moreover, most engine engineers will tell you that a modest amount of part-throttle ping bothers you more than it hurts the engine.
<<<

I do not totally agree with the article since it said the Ford engineers claimed it never pinged. I did hear ping on maybe a 4%, long hill, hot day and AC on, so summer time I went to 91 or even 89, if I was being cheap, The rest of the year 87 made no noises. I drove my SHO 120K miles without problems in the engine itself, and I was rarely gentle, that engine liked to wing it. The rest of the mechanicals were a well known issue tho. So I sold it. I have seen similar articles from time to time in various rags, so I assume there is some truth to it but may not apply on our LS engines. And of course don't believe everything you read.

More experimenting to do, I only have maybe 5K under the belt with the LS so lots to learn yet. Man I miss my totalled SS, it was so unfussy, but I also experimented in devious ways with it too.

Jim Henderson
 
And I'll throw another curve at you. I had a 428 FE in my 69 Mach 1 that I built with just slightly over 11:1 compression. The machine shop told me I was nuts with that compression ratio and the old school head design. Normally, they would be right. But I installed a bigger camshaft with enough overlap to bleed off combustion pressure and I NEVER had a knocking issue! That may very well be why your SS didn't ping on 87 octane.
 
captainalias said:
Jim, what year and engine LS do you have?

My LS is a 2004 V8 LS, with about 19,000 miles on it now. I bought it with 14,000 miles. It was broguht in from Hawaii(So assumed humid and low altitude. It now resides in So Cal, where during the time I have owned it since March, it has been either warm and rainy or hot, or damn hot and muggy with altitudes maybe 1,000 feet or less.

It has only run maybe a couple tanks of 87 with mild pinging only upa steep hill in about 4th gear, or once or twice I stomped on it and it knocked and stumbled. I have run mostly 89 since about May with no audible symptoms of ping, knock or detonation. I currently have 92 in it(after a run with 89) to further test whether 92 affects mileage.

I have kept decent vehicle logs since the early 80s. I like to keep track of what happens and make conclusions valid or not based upon those logs. So far so good.

Juts for reference, the LT1 engine in my 96 Impala, was essentially an all iron, "detuned" base model Corvette engine from that era. I am not sure now of the cam specs other than it was a milder version with lower lift and perhaps not as much duration. I did not tinker with that car since I and thousands of others, felt it was a classic and would appreciate, it was til some duffus rear ended me.

The article on why the LT1 was able to live with high compression pretty much leaned to the reverse cooling, ie cold water thru the heads first then the block rather than the usual engine first, heads next. And, the computer controls were set to detect and adjust for knock. I am assuming(maybe wrongly) that computer knock control is pretty standard now a days and is meant to optimize performance to the gas you are burning, along a zillion other things.

Jim Henderson
 
I bought midgrade 89 last time and didn't see any significant mpg decrease. No knocking. Oh well back to premium 93 this time (it's not much different with gas prices over $3 anyway ;))
 
FOR THE LOVE - stop - it's 91+ - period.

it's less than $0.13 a gallon difference = 18*13 a fillup = $2.34 per fillup

so at 20,000 miles per year @ 20mpg = 1000 gallons per year

so at 18 gallons per fillup = 55.56 fillups * $2.34/fillup = $130/year

so why is anyone fooling around for $130 per year (about $11/month)?
 
all i can say is i never have used less than 93 octane in my ls. the previous owner claimed to have used 89 with 93 for a short time. use 91+ everytime in my opinion.
 
Oh come on, you're really just mad because I dug up a 2 year old thread right? :D It's not like one tank of 89 in the car's lifetime is going to kill it.
 
nah - just ribbing you about saving 2 bucks - you have the money to replace the engine, so you can do things like this.

If I had all your cash - I'd burn mine..... ;)
 
I've been burning Fighting Cock Whiskey in mine exclusively for 9 months. I'm getting 7 miles to a fifth. A fifth is actually 1/5 of a gallon so, 35 MPG! :D

It's 103 Proof. Does anyone have a Proof to Octane conversion chart?:confused:
fightingcock15yo.jpg


One downside is getting pulled over by the police. I have to admit there is a slight "aroma" that the police don't like! When I tell them all the empty whiskey bottles in the back seat were used for fuel they break out the Breathalizer. Hmmm....I wonder what that would read at the exhaust pipe?:rolleyes:
 
Since the thread is brought back to life like a Zombie...

Now that I have 50,000+ miles on my 2004 LSV8 I can say the following...

I run 89 octane probably 70% of the time year round. I run 87 when it is cold and wet and I am feeling especially cheap, or on long easy road trips. I run 91 maybe 1 tankfull every few months. Contrary to what some people have claimed, my engine has not blown up yet, hell has not frozen over, heck global warming.

I will say for normal daily commute of 60 miles round trip with about 10 street, 5 stop and go and the rest at 50 to 80mph, the 89 works just fine. As far as mileage I haven't analyzed my log book in detail but it seems like If I am running 89 and then tank up with 87, the mileage actually goes up 1mpg or so. Then if I put in 89 it might go up again, but over the long haul I get about 18-19 mpg on my commute.

I am in SoCal so winter gas is different and of course the weather fluctuates from cool and wet to blazing hot and dry. So my mileage is almost surely varying due to weather and driving conditions. MAYBE it varies with octane, up to a point.

As mentioned in previous posts 87 will ping and or knock under hard acceleration especially in hot weather. 89 only has a gentle ping on occassion under hard acceleration. 91 never gives me problems.

On my daily commute I almost always accerate hard onto the freeways and somewhat hard at stop lights. Otherwise I am usually in steady cruise or stop and go.

I am guessing that my daily hard accelerations help "Clean out the carbon", which was my experience way back in 55mph days with my TA. My 79 TA would "clog up" over a couple months of 55mph and gentle driving. Once in awhile I would stomp on it and it seemed to clean things out. I am guessing this is maybe what happens with different member's LS. Some of us never clean it out and the engine will knock more easily. Just a theory.

Just my opinion,

Jim Henderson
 
i have only put 87 in both the seville with a V8 northstar with 140,000 mi (runs great) and in the lincoln. the CTS-V only gets 91 because that does knock if i put anything less.
 
I don't understand why people mess around with cheap fuel. The LS has a high compression engine, so due to the laws of physics, it needs high octane fuel. Full stop. No amount of justifications ("I ain't never noticed no pingin'") will change that. Not only will you not get as good mileage, meaning you spend as much or more per mile on fuel, but you will also risk engine damage. But no, go ahead and mess with your engine. One of these days someone in a 300 or a CTS will pull up next to you at a light and you will decide to show them what your car can do, and when you put it to the floor and hear that fuel detonating everywhere but in the cylinder, you'll understand why it says "91+" on the gas cap.
 
I average about 15K per year.

I experiment because I like to. And I perhaps foolishly think I can tell the tune of an engine and when you should back off.

I have only heard true detonation once in my life on a car I was playing with a beater VW belonging to a cousin. other times were at the track and don't count. Most of what we hear is pinging and knocking, detonation is rare. These are shades of grey from harmless to disasterous. If you have detonation you got a real problem and should stop immediately. Knocking is bad but usually fixed with octane. Ping can be totally harmless to longterm harmful if constant. Old non-computer engines had much more trouble with octane than we do now.

The real difference in cost is really insignificant. Running 91 IS the safe bet. I make my comments just because we know some are curious and will try it no matter what is said. I don't think this engine will blow up unless it is on the ragged edge of death at 200K miles and loose as a goose. If it does blow up it will be the first of my vehicles to do so and I have treated other engines much worse.

In over 35 years of driving, tinkering, and abusing my cars, I have never blown an engine because of gas or anything else for that matter, but surely my day is coming. In my opinion, an engine in good condition and proper tune with correct equipment can take much more abuse than we give it, most manufacturers test under much harder conditions than we see and then build in a margin. 91 octane I believe is one of Ford's margins, NOT a bad thing. Bad maintenance is where I think engines die.

Worst come to worst, I think if a CTS wants to race me while I have 89 in the tank, I may lose. But then I am not in the habit of racing just everybody, not easy or safe to do in LA area. For every day driving, the engine computer shoudl be able to manage things assuming the engine etc are in good condition. If you race all the time, that is different and usually excluded in warranties.


Just my opinion and everyone's mileage and experience will vary,

Jim Henderson
 
well said - and your making a educated choice.

It's not much in cost savings - at 15k a year is less than $10 a month - and loosing your ability to put your foot in it is wasting a V8 at times...

me - no choice - 93 that how I'm tuned and that all I can do - and my foot's in it alot.
 

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