Firebird V8-305 5.0L VIN F FI (1987)
Engine Oil: Technical Service Bulletins
Engine - Oil Recommendations
Number 84-6 (Gasoline)-26
Date 3/84
Subject:
ENGINE OIL RECOMMENDATIONS (FOR PASSENGER CARS)
The purpose of this bulletin is to:
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advise you of the reasons for changes in engine oil viscosity recommendations, and
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explain the new API service symbol which should assist vehicle owners in finding engine oils recommended for GM engines.
Gasoline Engine Oil Viscosity Recommendations
Since 1980, the preferred viscosities for GM gasoline engines are SAE 10W-30 for the larger engines and SAE 5W-30 for the smaller engines (engines
sizes defined later).
SAE 10W-40 is not included in the viscosity chart for 1984 GM gasoline engines, for several reasons, including:
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Fuel economy with SAE 10W-30 oils is about 1 percent better than that with SAE 10W-40 oils.
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SAE 10W-30 oils generally produce less piston and ring deposits than SAE 10W-40 oils. Such deposits can lead to stuck rings and increased oil
consumption.
The use of SAE 10W-40 engine oil in a vehicle equipped with a gasoline engine will not automatically void the General Motors Corporation New Car
Limited Warranty. However, since SAE 10W-40 engine oil is not recommended for use in 1984 GM vehicles equipped with gasoline engines, if the use
of such oil causes damage, the cost of the engine repair will not be covered by the Warranty. The Warranty does not cover any damage due to the use of
non-recommended oils, whether SAE 10W-40 or some other viscosity. In addition, the Warranty does not cover damages caused by the use of oils that
do not meet the recommended API quality or SAE viscosity grade.
Diesel Engine Oil Viscosity Recommendations
Preferred viscosities for diesel engines in GM passenger cars are SAE 30 for the larger engines and SAE 10W-30 for the smaller engines.
SAE 10W-40 oils have never been recommended for diesel engines in GM passenger cars. Nevertheless, some owners have used SAE 10W-40 oils and,
in some cases, experienced engine damage caused by excessive piston and ring deposits. In an effort to clarify the GM recommendations for passenger
cars, the 1984 owner's manuals state specifically for diesel engines "DO NOT USE SAE 10W-40 GRADE OIL, OR ANY OTHER GRADE NOT
RECOMMENDED".
If damage to a GM diesel engine is caused by the use of SAE 10W-40 engine oil, the cost of the engine repair will not be covered by the Warranty.
API Engine Oil Service Symbol
A new API service symbol is being used in GM owner's manuals and on oil cans. Urge your customers to look for it in their manuals and on the
containers of the oil they select for use in their cars. These are examples of the symbol:
The symbol has an upper segment, center area, and lower segment. An explanation of the information in each of these locations is as follows:
Upper Segment:
QUALITY LEVEL
API (American Petroleum Institute Service Categories
