hey
I have a 92 RS with the 305 tbi, my mods are LT1 cam, dual snorkel air cleaner, 3 inch exhaust, and 3.73 gears

what level octane should I be using at the pump? still 87??
by the way my timing has been bumped up to 6 degree's.

 

you should use the lowest octane you can get away with, wihtout the engine pinging or knocking. try some 87 octane and go from there. do some hard acceleration, such as flooring it while going up a steep hill, and listen for any knocking and pinging. if it knocks, try a little higher octane.

 

Yeah this is always a car to car basis....the owner manuals for pre 88 say an 87 octane is preferred anything less is garbage...but ive always had good times running plus (91)....its a few more cents than regular and yeah the extra cents do make a difference but put like 5 dollars regular (87) in it and see if it makes the engine knock...if it does youll get worste gas mileage than using a premium octane...something with the computer and timing but its too frikkin early to go in depth....when in doubt go with the plus

 

Exactly, a lot of people waste their money on premium when they don't need it.

 

I tried two tanks of regular and two tanks of super in my 92 LO3, to see if my mileage changed. This was back about two years ago when gas was cheap though. I found that my mileage went down the toilet if I used regular, as opposed to super. How much of a difference?? I did the math and it came out costing me MORE money to fill the tank with regular because I wouldn't get my 325 miles per tank. Not to mention the side effects like low idle, hotter temps, and risk of detonation. Probably something to do with my mods as well, but still, I thought that was interesting. I think the biggest issue is the timing- you can use regular if you don't go too far past stock settings.