hi all, i have lt1 and right now i am running 87 octane in it and the manual says it is supposed to run 91 octane, or the car accellerate slower, the question is would it be ok to mix the two fuels, i usually dont run it past the 1/4 mark cause i dont know how reliable the guage is, so would it be ok to top it off with 91 octane with the tank 1/4 full of 87. and what do they mean accerate slower, do they mean more hesitant?

 

The easy answer is yes. The car "can" run on 87 octane, but you run the risk of detenation. And of course it will be slower and not get as good as MPG.

 

And the answer to the question you actually asked is also yes: its safe to mix the fuels. Actually, 89 octane from the gas station is (usually) a mixture of 87 and 91 (or 92/93/94/whatever they have for premium).

When they say slower, they mean slower. Less horsepower and torque because the engine backs off on the timing to avoid predetonation.

 

so is that mabe the reason its alittle hesitant when i step on it, its not really that bad but it is noticeably sluggish

 

How about you just put the premium in like you're supposed to? Spend the extra $1.80 on a tank and have a car that runs correctly. If you can't afford the extra buck eighty then maybe it's time to trade your car in for a 1986 Yugo.

 

Here's the problem. Your timing is getting retarded by the computer because of detonation occuring in the cylinders. Detonation is hard on the bearings and rotating assembly. Even though the computer is retarding the timing there is still some detonation going on that the computer is picking up on in order to retard the timing. Why would you want to risk subjecting your engine to this? I recommend using premium like it is suggested.

 

87 in an LT1?

 

Top it off with the 91 or 93 octance and continue using that for now on.

 

well it kinda doesnt help when my car didnt come with a manual, so that is why im asking, yeah sure the 91 or higer octane is more expensive but i could shell that out as apposed to spending another 2-3 grand rebuilding the motor agian

 

Low-octane gas does not, IMO, explain the "sluggishness" that you describe. Take your car to a mechanic you trust and have it checked out. Plugs, OptiSpark, fuel filter, fuel pump... there are tons of things that can cause the behavior you described, but the retarded timing from running 87-octane isn't one of them. That will just make the car a little slower -- it should still be just as responsive.