Knock retard

[shooterc5]

Sorry guys im relatively new to this and full of questions. So here is another one. :-) I usually run regular gas in my 99gtp (Because gas is freaking expensive). Its all stock except for the FWI. Is there any knock retard when using regular gasoline being its a stock engine? Or am i just doing a bad thing for the engine and not let letting put out its full potential at this point? Ive its ok to use regular fuel with a stock engine but ive also heard always run premium. If someone could explain this to me i would really appreciate it. I want to get the most out of my GTP.

[Ripn12s]

Every car is different on how much KR you'll see. Only real way to find out is to scan the car. I'd say more then likey though that you are seeing some KR.

I'm cam'd w/ 3 deg kr on 93 oct and still every once in awhile I'll run 89 octane. Just have to realize you cant beat on it.

[rubberman]

$1.85/gallon for 87 octane X 18 gallons = $33.30
$2.05/gallon for 93 octane X 18 gallons = $36.90
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Difference of only $3.60 to fill up. If you look at it that way.

[carnutcass]

I agree....the price per gallon difference looks huge but the total bill for a tank full isn't that much more. I know a couple of guys who have cracked pistons as a result of too much knock. I'm not sying that's gonna happen to you, but is it worth the risk?

[GTPWarrior]

I have even notice a huge difference in my 98 GTP
from when I use regular and premium and it eventually cost me an additional 50 to get my lines cleaned out.
I think your better off paying the extra 3+ bucks.
This probably doesn't answer your Q but its just what I have noticed.

[GTP Dad]

I agree with GTPWarrior, spend the extra money for the premium gas. Anytime you apply boost to an engine if the octane is too low you will get significand detonation and will damage the engine. I would much rather pay the extra 3 bucks on a fill-up than the 2-4k dollars to replace the engine when things start breaking.

[richtazz]

most GM supercharged 3800's require premium fuel. The boost essentially raises compression ratio, and running low octane in a high compression engine is asking for disaster. The money saved is not worth the risk involved. Stick with the recommended octane, and don't be cheap, or it could come back to bite you in the ass. My mother-in-laws P-Ave ultra dropped from 19-21 mpg to 14-15 mpg when she tried to switch to 87 octane, so it ended up costing more to run the cheap gas when you factor in the crappy mileage using the cheaper fuel.

[Mr. Cynical]

This is a subject that's near and dear to me.

When I lived in Chicago, I always put 93 Octane fuel in my 99GTP. Now that I'm in Denver, the best I can find (aside from the 100 octane gas that's literally a block away from my office) is 91.

So, what I'm curious about is this: Aside from general lower performance due to less O2 in the atmosphere here, am I risking KR by filling up with premium? I just don't understand enough about how it all works to know for sure.

If it makes a difference, a few weeks ago, I had my car scanned, and the person who did it said there were absolutely zero codes blown.

[richtazz]

a lower octane fuel is more volatile than a high octane fuel. This causes the fuel to ignite due to residual heat in teh combustion chamber. high octane fuels burn more evenly, and resist pre-ignition, leading to less spark knock. Higher octane fuels have no advantage to a vehicle that doesn't need them. The old myth that high octane means more cleaners/detergents is just that, a MYTH. But if your car REQUIRES higher octane, not using it can grenade your engine, especially under hard load, heavy footed driving. In your case Mr. Cynical, it's even more important to run the proper fuel, because of the less dense atmosphere in the mountains. in a nutshell, detonation=death. So don't be cheap, and buy the fuel yor owners manual recommends. In your case Mr. Cynical, get the best you can.