OIL ECONOMY (USAGE) GENERAL GUIDELINES

VEHICLES AFFECTED: All

We have received dealer requests for information they may use to advise owners 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 car 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 consumption for the smaller size engines used in todays 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 litre every 3 kilometers. 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 car that has run 1600 kilometers 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 car then might be driven at high speed on the highway, the dilution elements boil off rapidly and the car appears to use two quarts of oil in a hundred miles.

'Car owners should expect increased oil consumption at high speeds. No standard rate of consumption can be established because under various combinations of the engine sizes and conditions mentioned above, one engine might use a litre in 3500 kilometers and another use a litre in 2100 kilometers 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 until it has run at least 6500 kilometers.

Keeping the above information in mind, be certain that the customer is using the oil recommended in the Owner's Manual. It is essential they use the correct viscosity oil for the climate condition encountered by the car. 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.