For the longest time i ran 87 octane. the previous owner told me to use 93 octane for lb9 5speed.

I am rebuilding it now and am curious if it makes a difference in which one to use since I never felt a difference in power economy etc. before? Will I damage anything with 87?

I beleive it is 10.5 to 1 compression.

 

Hello 88formula305tpi!!

The owners manual for a 1987 Camaro with 5.0L (F) or 5.7L (8) states: "Your engine is designed to operate on premium grade unleaded fuel. However, with the electronic spark control system, you may use regular unleaded fuel at slightly reduced acceleration performance". "You should use a premium unleaded fuel with an octane rating of at least 91. You may use a regular unleaded fuel with an octane rating of at least 87 at slightly reduced acceleration performance"!!



There is no reference to whether or not the car has an automatic transmission, or is a 5 speed, as that doesn't matter. It's the engine that requires the octane, and not the transmission!!

A good rule of thumb is to use the lowest octane rated gasoline that you can get away with, that won't cause your engine to have spark knock.

 

What does spark knock sound like, because I never heard it before. Im guessing becuase the timing is retarded to avoid this.

 

Hello 88formula305tpi!!

If you can hear it, it sounds like a metalic rapping sound!!! Like a bunch of tiny little hammers beating the crap out of your motor!!!

Your guess above is right, the electronic spark control system will retard your timing to avoid the knock once the knock sensor picks it up!!

Basically, the timing is retarded a whole bunch once the knock is detected, and then it's advanced up to the point just where the spark knock is not detected!!

Using higher octane gas helps control spark knock also, and aids in the performance of your engine, however, using too high of an octane gas, just wastes money, as the higher octane is not needed!!



Personally, my 1987 IROC-Z 305 TPI 5 speed gets nothing but 94 octane (one tank of 87 octane in September 1994, couldn't get 94 octane in the one pump town), she "feels" smoother, and performs great!!

My money, my choice how I "waste" it!!

 

It should run fine on 87 octane, stock from the factory. If you now have 10.5:1 compression (factory was not that high)... then probably not.

 

Hello madmax!!!

He said he "believes" that it has 10.5 to 1 compression, which would call for a higher octane gas.........but, if he employed the stock engine ecm/sensors, he could probably get away with the 87 octane gas, although it would lack some performance.