I've got a 5 gallon can sitting in my Dad's shop right now that I got from Sherwin Williams for ~$30.

And I'm down to the 1/4 tank I wanted to be at before adding a gallon of toluene to the tank.

For a grand prix with an 18 gallon tank, already using 93 octane gas, the equation for the toluene is;

(558+7x)/6=y where X is gallons of toluene and Y is final octane rating.

Note that this equation will ONLY work with 93 octance gas in an 18 gallon tank. If you have a different car, you will need a different formula.

I'm going to go to the gas station now and we'll see what happens... BBS