It should not be too viscous, as the starter must crank the cold engine so that after a cold start, the oil immediately reaches all lubrication points.
It should not be too thin, because at high temperatures and speeds, breaks may appear in the oil film.
The graph shows recommendations from Audi/Volkswagen regarding oil viscosity:
- A - all-weather oils according to the VW 500 00 standard;
- B - all-weather oils according to the VW 500 01 standard.
The named parameters are understood as long-acting temperatures. Short-term fluctuations do not play a role.
Oil classes according to SAE
Society of Automotive Engineers (Society of Automotive Engineers, USA) divided all oils according to the degree of their viscosity into classes. Motor oil classification starts with liquid winter oil (winter) SAE 5 W, 10 W, 15 W, then SAE 20 W/20 intermediate stage and ending with viscous summer oils (Summer – Summer) SAE 30, 40 and 50.
Seasonal oil
The cheapest motor oil used to be seasonal oil. For optimal lubrication of the engine, thick or thin seasonal oil must be poured into it according to the season. Now seasonal oils are almost not sold (I mean Germany), but they are still often used in fleets. The use of seasonal oil in the Audi A4 is not provided.
All-weather oil
More labor-intensive to manufacture and therefore more expensive than seasonal oil, all-weather oil has found the widest application today. To improve the viscosity-temperature properties (VI) it contains as an additive long chains of molecules that swell when heated and shrink again when cooled. In this regard, the oil can plastically adapt to temperature and, according to its characteristics, cover several viscosity classes. Oil SAE 15 W-50 at -15°C corresponds to a viscosity class of 15 W and at 100°C to class 50.
All-weather oils of SAE 10 W-30 and 10 W-40 classes are not recommended for use in Audi engines during the warm season.
Visitor comments