ACDelco X66P Fuel Injector and Upper Engine Cleaner - 16 oz Product has multiple service applications - effective for in-rail fuel injector cleaning, intake valve/port and combustion chamber deposit removal, and piston top soaking clean-up Designed to maximize engine performance - use may help restore lost power, smooth out rough idling, minimize hard starting, reduce octane requirement, and minimize intake and exhaust valve sticking Assists in the elimination of deposit-related carbon rap, knocking, pinging, hesitation, stalling, and engine run-on