GASOLINE ADDITIVE EXHAUST VALVE RECESSION

MODELS AFFECTED: PRE-1971 PASSENGER CARS

Some engines designed to use leaded gasoline may experience exhaust valve recession if operated at high speeds and loads with unleaded gasoline. Therefore, if leaded gasoline is not available, or if additional protection is desired with low-lead gasoline, the GM Anti-Valve Recession Additive, P/N 12345492, may be used. The recommended dosage is one container per tankful (20 gallons) of unleaded gasoline, which should provide valve protection equivalent to leaded gasoline with a lead concentration of 0.1 grams per gallon.

NOTE: Additive should not be used in engines designed to operate exclusively on unleaded gasoline (with restrictor in fuel tank filler neck).

As a reminder, pre-1971 engines were designed to use a fuel with a minimum octane rating of 89 R+M/2 (average of Research and Motor octane numbers). If unleaded fuel is used, be sure that it has an octane rating of at least 89 R+M/2.

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.