How Bad Is Putting Under 91+ Gas?

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v-teg

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just wondering how much damage does putting under 91+ gas in the v8 LS does to your cars engine?
 
I'm sure you won't blow your engine, the ecu will compensate for the lower octane and retard timing to make it run safe, I wouldn't recommend it though.
 
Don't do it. It can lead to blown coils. That's my experience at least. If you did it by accident throw a bunch of octane booster in.
 
KD00LS said:
Don't do it. It can lead to blown coils. That's my experience at least. If you did it by accident throw a bunch of octane booster in.
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the dude i bought the car off of i can def tell he was using less than 91 because i had to change the coils
 
Octane has nothing to do with the coils failing. The coils are cheap, they failed on their own, it happens to EVERY LS.

You can run a lower octane but it is NOT recommended for these engines. The main thing that happens is the compression of the engine combined with some heat will cause the fuel/air mixture to partially combust before the spark plug fires giving you a condition known as Pre-detonation, or spark knock. This detonation usually happens before the piston reaches the top of its travel, and it will put force on the piston to push it back down, just the wrong way. This puts extra strain on the piston, wrist pin, and connecting rods, as well as the crankshaft and the rod bearings. If this happens often enough it will eventually wear out one of those parts (usually the wrist pin or connecting rod) and it will break. Which then means you have to buy a new engine.

If you are a careful driver and don't use much throttle during your daily driving, and don't live in an area with lots of hills, then you can avoid spark knock pretty easily and you would probably be safe using 91 or even 89 instead of 93. But I wouldn't recommend it.
 
LS8 said:
I'm sure you won't blow your engine, the ecu will compensate for the lower octane and retard timing to make it run safe, I wouldn't recommend it though.
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+1

Dirty up your vavles, knocking, pinging.
 
97stscaddy said:
Octane has nothing to do with the coils failing. The coils are cheap, they failed on their own, it happens to EVERY LS.

You can run a lower octane but it is NOT recommended for these engines. The main thing that happens is the compression of the engine combined with some heat will cause the fuel/air mixture to partially combust before the spark plug fires giving you a condition known as Pre-detonation, or spark knock. This detonation usually happens before the piston reaches the top of its travel, and it will put force on the piston to push it back down, just the wrong way. This puts extra strain on the piston, wrist pin, and connecting rods, as well as the crankshaft and the rod bearings. If this happens often enough it will eventually wear out one of those parts (usually the wrist pin or connecting rod) and it will break. Which then means you have to buy a new engine.

If you are a careful driver and don't use much throttle during your daily driving, and don't live in an area with lots of hills, then you can avoid spark knock pretty easily and you would probably be safe using 91 or even 89 instead of 93. But I wouldn't recommend it.
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def some good info thanks......lucky i havent heard none of that knocking or pinging
 
Ok, I have to eat a few of my words here. Found THIS article which explains the difference between Pre-ignition, which causes pretty much instant engine failure, and detonation, which takes a while longer, but can still kill your engine. Very good read. Both can be caused by using lower octane fuel than what is recommended.

Pre-ignition happens before the spark, usually long before the spark at the very beginning of the compression stroke.
Detonation happens after the spark and the noise that it makes is caused by the rapid pressure spike inside the chamber.
And detonation can lead to pre-ignition if allowed to go on for long enough.
The article gives MUCH more detail on this subject.
 
We've been running 87 octane in our '03. What I've been noticing, is a lot of tip-in detonation (it rattles for just a few tenths of a second when you open the throttle quickly). Cruise and WOT don't seem to make any audible detonation. I didn't ever notice the noise until I ran a few tanks of premium. I wonder if this because of some adaptive strategy?
 
97stscaddy said:
you would probably be safe using 91 or even 89 instead of 93. But I wouldn't recommend it.
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91+ is recommended. So 91 will be just fine.

Also, not everyone in the country has 93 available.


I always say, if you can afford the car, you should be able to afford the gas. Its not THAT much more than regular. Especially when you consider the cost of the damage you may cause.
 
v-teg said:
def some good info thanks......lucky i havent heard none of that knocking or pinging
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Maybe it was just the straw that broke the camels back but as soon as I put 87 in the tank the coils blew. Happened twice.
 
Another consideration is what altitude you live, higher altitude higher the octane is needed. I live at 4,300 ft above sea level; using anything less than 91 sounds like a diesel. As V-8 stated about availability, 93 octane is an east coast thing and 91 are more common in the west. I use what Lincoln used for developing the LS, 91 octane.
 
When I bought mine my engine started misfiring. I found out later the dealer put 87 in it. Then I put 89 in it a few weeks later and my check engine light came on saying my cat is malfunctioning. I think it caused another problem. Its only a dollar more a tank so I would put 91 and up in there.
 
gcwimmer said:
Another consideration is what altitude you live, higher altitude higher the octane is needed. I live at 4,300 ft above sea level; using anything less than 91 sounds like a diesel. As V-8 stated about availability, 93 octane is an east coast thing and 91 are more common in the west. I use what Lincoln used for developing the LS, 91 octane.
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yea im out in boston so 93 is everywhere over here 30 cents more compared to 87..... but worth having more car break down
 
i ran 89 once instead of 91+

if u put in 15 gallons, and its 10 more cents...thats only 1.50 more lol.

I noticed the car didnt run as smooth and quietly, could hear alot more of the engine at idle. its still alive tho
 
can using a lower octane affect gas mileage at all? i stick with 93 becuase the next closest i can usually find in orlando is 89 and thats not worth the trouble that comes along with lower octane fuel.
 
gcwimmer said:
Another consideration is what altitude you live, higher altitude higher the octane is needed. I live at 4,300 ft above sea level; using anything less than 91 sounds like a diesel. As V-8 stated about availability, 93 octane is an east coast thing and 91 are more common in the west. I use what Lincoln used for developing the LS, 91 octane.
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We have 93 in the Midwest here in Missouri!
 
No 93 available here, next door in Kansas...91 is as high as they sell, (if you're lucky)....some stations only go up to 89.
 
93 always. I would buy 91 if I could find it around. I've been on Sunoco's second highest octane (93). Once I get back home, I'm gonna switch to Chevron's premium.
 
cny85 said:
When I bought mine my engine started misfiring. I found out later the dealer put 87 in it. Then I put 89 in it a few weeks later and my check engine light came on saying my cat is malfunctioning. I think it caused another problem. Its only a dollar more a tank so I would put 91 and up in there.
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I gota Call 'Shenanigans'
putting 87 isn't going to kill your cats . age and old poor running motors kill cats ...... we don't have leaded Gas anymore that isn't meant to be run in CATS

With 87 you may not be the in front of the pack always .
 
Down in west texas there is absolutly no gas stations that sell more then 90 octane.. what is with that? i drove for a year all over the US and i was extremly pissed that texas didnt have higher then 90.. talk about bull....

how come no one has ultra 94? no gas station that i have seen in the US has it but in canada at Sunoco they have it.. 4 more cents then premium. I use it all the time... the performance if through the roof... some people say it dosent help but going from 90 to 94 octane it helps big time
 
Try using the search function since this has been discussed plenty of times and the opinions hardly ever change.
 
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