- 1. SAE viscosity grade.
- 2. Quality level according to API or SSMS or MTS; the most common is the API scale.
The table illustrates oil viscosity recommendations for intake diesel and turbodiesel engines. The indicated temperatures are to be understood as permanent. Small short-term fluctuations do not play a role.
Diesel engine oil specification
Oil specification for turbodiesel engine
Firm "Volkswagen" prescribes API CF oil for turbodiesel engines. For topping up between shifts only, API CE oil can also be filled if oil of the named quality level is not available.
Oil viscosity
The viscosity of an oil determines the following:
- will the starter be able to start a cold engine;
- will all lubrication points be provided with oil after a cold start;
- oil film strength at high temperatures and speeds.
The American Automobile Association has classified oils into classes according to their viscosity: from low-viscosity winter oils SAE 5, 10.15 to intermediate stage SAE 20 and then to thick summer oils SAE 30.40 and 50.
The cheapest is seasonal oil. For good engine lubrication, the oil should be low viscosity or thick according to the season. This means that winter oil should be poured into the engine in autumn, and summer oil in spring.
Essentially more expensive and more labor-intensive to manufacture is all-weather oil. It contains additives. Thanks to this, the oil can flexibly adapt to a particular temperature and comply with several viscosity classes. Oil brand SAE 15W-50 at -15 degrees Celsius corresponds to a viscosity class of 15, at a temperature of 100 degrees Celsius -class 50. There is a problem due to the fact that some multigrade oils may change properties over time. Then the upper viscosity class can no longer be maintained, the oil is no longer so resistant to temperature. For this reason, multigrade oils of SAE 10W-30 and 10W-40 classes are not recommended for engines during the warm season "Volkswagen".
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