Maxima 83916 Hi-Test Octane Booster - 16 oz. Bottle Hi-Test is an all organic concentrated octane booster containing no metal (lead, manages or phosphorus) compounds, legal for all types of competition, and readily mixes with all gasoline as well as alcohol or nitro mixtures Hi-Test will suppress detonation and pre-ignition by modifying the burn rate and increasing the auto-ignition temperature of the air/fuel mixture The use of Hi-Test in your gasoline will eliminate pinging and knocking and the potentially destructive results of them allowing for higher compression ratios and therefore more horsepower Hi-Test should be used in concentrations of one to four ounces per gallon of gasoline, one ounce per gallon raises the effective octane number approximately four points, depending on the base gasoline octane For racing or very high compression engines, or very low quality fuel, higher concentrations of Hi-Test may be required