Wholesale Johnsens Octane Booster Johnsen's Octane Booster is formulated to stop knocking caused by low octane fuel. It may be used in any grade of gasoline-- just add to gas! Special additives increase octane and clean fuel system. Johnsen's Octane Booster does not contain alcohol and is safe for catalytic converters and oxygen sensors. 7 fl oz per bottle, 12 bottles per case.