OIL ECONOMY (USAGE) GENERAL GUIDELINES. GMC Truck S15 Pickup - 2WD 1985

For 1990-2009 cars

# OIL ECONOMY (USAGE) GENERAL GUIDELINES

#### MODELS: ALL LIGHT DUTY WITH GASOLINE ENGINES

Requests have been received from dealers for information that may be used to advise owners of what is considered normal oil economy in today's engines. What is normal oil consumption can best be answered if specific driving conditions to which a vehicle is subjected are known. It is similar to asking, what is the normal fuel economy for any given model. If there were not so many variables involved, a simple specific statement could be offered.

The information below is in agreement with our Engineering Department, and since it is a down-to-earth reply, we are hopeful that it will be useful in answering owners' inquiries concerning oil con- sumption for the smaller size engines used in today's products.

"A gasoline engine depends upon oil to lubricate the cylinder walls, pistons, and piston rings. When the piston moves downward, a thin film of oil is left on the cylinder walls, and on the firing stroke, it is burned by the flame of combustion. For example, if an engine were to burn as much as one drop of oil every firing stroke, then it would use more than one quart every two miles. Modern engines use much less oil than one drop, but all efficient engines use some oil. If they did not, they would quickly wear out."

"The rate of oil consumption depends upon engine sizes, the quality and viscosity of the oil, the speed at which the engine is operated, the temperature, and the amount of dilution and oxidation which takes place. These conditions are frequently misleading. As an example, a vehicle that has run 1,00 miles or more in city operation, may have consumed a normal amount of oil, yet actually measures up to the full mark due to dilution (condensation and fuel) in the crankcase. The vehicle then might be driven at high speed on the highway, the dilution elements boil off rapidly and the vehicle appears to use two quarts of oil in a hundred miles."

"Vehicle owners should expect increased oil con sumption at high speeds. No standard rate of consumption can be established because under various combination of the engine sizes and conditions mentioned above, one engine might use a quart in 2,500 miles and another might use a quart in 1,500 miles and yet both engines might be normal."

"New engines require considerable running time before the piston rings and cylinder walls become 'conditioned', and during this time they use oil more rapidly than later. An engine's oil economy should not be judged untit it has run at least 4,000 miles."

Keeping the above information in mind, be certain that the customer is using the oil recom mended in the Owner's Manual. It is essential that they use the correct viscosity oil for the climate condition encountered by the vehicle. Also, the container of the oil to be used should be labeled for Service "SF" which is currently specified in our Owner's Manual.

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.