For regular grades of unleaded & leaded gas. STP Octane Booster boosts octane and cleans combustion chambers to allow cars to perform more like they should. Regular use helps boost octane, stop knock & ping, restore horsepower, clean fuel intake system, prevent hard starting and stop engine run-on. Plus! The two active ingredients work to help improve sluggish performance, reduce hesitation, smooth rough idle, and eliminate stalling. Contains no alcohol. Safe for catalytic converters and oxygen sensors. Safe for use with other STP fuel additives.