Oil Consumption, Explanation

Group: 17

Number: 94-02

Date: Aug. 1, 1994

Subject:
Oil Consumption, Explanation

Model(s):
All Models, All Model Years

Engine oil serves many purposes in the internal combustion engine:

^ A dependable lubricant for all sliding and bearing surfaces.

^ Acts as a coolant and dissipates heat.

^ Ensures cleanliness through detergent action and filtration.

Even an efficiently running engine consumes oil or it would quickly wear out. All of the engine friction surfaces are cushioned by a thin film of oil. The upper piston ring (compression ring) for example, is lubricated by a thin film of oil deposited on the cylinder wall. This microscopic film is burned away during combustion. Although very little oil is consumed per stroke, over long distances small amounts can add up to whole quarts of oil. For this reason the oil level must be checked regularly.

The amount of oil an engine consumes depends on how the vehicle is driven. This is especially noticeable during the first 7500 miles when a new engine is being broken in and the internal components are seating.

Some factors affecting oil consumption are: the ambient temperature, engine size, quality and viscosity of the oil and the way the vehicle is driven.

When a vehicle is driven at highway speeds, unburned fuel, by-products of combustion, condensation and contaminants evaporate through the crankcase vent system and are consumed via normal combustion. A vehicle driven for short trips without fully warming up the engine or in cold weather may not appear to consume any oil because unburned fuel, by-products of combustion, condensation or other contaminants will mix with the oil and give the appearance that no oil is being consumed. In some cases, the added contaminants will even cause the oil level to rise significantly.

The best conditions under which to check the oil level are with a warm engine on a level surface. When checking the level with a warm engine, it is recommended that the engine sit for five to ten minutes with the ignition switched off. This allows the circulated oil to drain back into the oil pan for an accurate reading.

Always use the correct API and SAE rated oils for the specific driving and environmental conditions the vehicle will experience, as recommended in the Audi Owners Manual.

Always change the engine oil at the intervals specified in the Audi Maintenance Manual.