If you want to raise the octane rating a little to be able to advance the ignition timing, and still be able to run 87 octane gas, add 5% Diesel fuel to the mix- - - -1 gallon of Diesel to 19 gallons of gas. It raises the specific gravity of the fuel, slows down the burn rate, and allows the initial timing to be advanced an extra 5 degrees or so without getting detonation. It's a trick we used on the round track cars when we ran straight pump gas with blue machinists' Dykem added to mimic the blue-dyed gas the track sold at an outrageous markup.
Jerry
