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Oil Consumption, Measure

General

The oil consumption of a combustion engine is defined as the volume of oil which is consumed as a result of the combustion process. Under no circumstances must oil consumption be confused with oil loss occurring as a result of leaks at the oil pan, cylinder head, etc.

The task of the engine oil is to:

1. Separate surfaces that slide on one another with an oil film, i.e. prevent dry friction;
2. Conduct the heat produced by friction away;
3. Conduct combustion residue away.

These tasks consume a certain amount of oil; in other words, the frequently expressed expectation that, as combustion engines continue to develop, they will eventually not consume any oil at all, is completely false. However, external operating conditions, driving style and manufacturing tolerances do affect oil consumption to a certain extent. Care should be taken to ensure that the oil level does not go below the "MIN" mark or exceed the "MAX" mark on the oil dipstick.

As oil consumption is a technical necessity, indications that an engine is not consuming oil mean that it is reasonable to conclude that the oil is being diluted by particular operating conditions. Frequent cold starts, driving when over-cold, etc., lead to the oil returning to the oil pan conducting fuel particles and condensation, and thus becoming "diluted"; this can lead to the incorrect supposition that the engine is not consuming any oil at all.

Oil diluted in this fashion lacks lubricating power and may lead to engine damage if the specified oil change intervals are not observed. The main causes for oil dilution are driving in mainly urban traffic and frequent driving at insufficient engine rpm when the engine is cold.

The oil consumption first begins to stabilise after operating for a few thousand kilometres; therefore, measurements of the oil consumption only become realistic after about 7500 km / 4000 miles. Before measuring the oil consumption, ensure that the engine is not losing oil due to leaks.

Note:   The oil dipstick can only be used for checking and not for measurement. The engine must always be switched off for at least 2 minutes before an oil level check can be performed. If, after an oil change, the maximum engine oil top-up does not correspond to the maximum level mark on the dipstick, this can be attributed to manufacturing tolerances.

All information regarding the permissible engine oil consumption and filling quantities are included in the Owner's Manual.

Measuring Method

1. The check is carried out with the vehicle on a horizontal surface with the engine at operating temperature (engine oil temperature min. 80 °C / 176 °F).
2. Drain engine oil immediately after switching off engine – draining time approx. 30 minutes (this value was determined experimentally).
3. The drained engine oil quantity is measured in a measuring container 1) and fresh oil added to the maximum engine oil filling quantity, minus the volume for the engine oil filter that has not been changed.
4. Using this amount of engine oil, the customer should drive at least 1000 km/625 miles without of course topping up the engine oil (the driver should keep to his normal routes and driving styles).
5. The procedure described above (points 1 to 2) is then repeated with exactly the same time for draining engine oil.
6. The quantity of engine oil "missing" from the measuring container is the engine oil consumption with respect to the distance travelled.
7. The oil consumption is calculated as follows:

filled oil quantity (l) – drained oil quantity (l)

x 1000 = oil consumption (I/1000 km)

distance actually driven (km)

1 ) with a capacity of at least 6 litres and a scale.
Related Literature Units
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Timing, Check > < Oil Pressure, Check