Oil System 67 Oil Consumption Once the engine is stopped, check the oil level daily. If the engine has just been stopped and it is warm, wait approximately five minutes to allow the oil to drain back to the oil pan before checking. Add oil as necessary. Note: DO NOT overfill. Oil may be blown out through the engine breather tube if the level is too high. All diesel engines are designed to use some oil, so it is normal to add oil periodically. An engine used in heavy duty operation will use more oil than one in normal operation. Owners often ask what is considered “normal” oil consumption. This is dependent on the operation of the engine.
Just as one engine in a heavy operation may get only 5 mpg fuel consumption and another gets over 8 mpg, the oil consumption will vary in different applications. To determine “normal” oil consumption, it is therefore important to establish what is normal for your engine in your application. Establish a record of oil usage and compare with other vehicles in your fleet. There are two methods that are frequently used: Miles per quart of oil. Simple way to establish a history of the consumption. Useful as a comparison to others only when vehicle and engine is compared to an identical vehicle and engine under identical operating conditions.
Amount of fuel used per amount of fuel used (oil consumption relative to fuel consumption). Better way to relate the oil usage to the actual work of the engine. Also only useful in comparison when compared under identical conditions.