Engine oil is strongly heated in its function as a lubricant in the engine. Therefore, it is particularly important to consider the correct viscosity when choosing the engine oil, because this classification of viscosity is strongly dependent on the prevailing temperature: The hotter it is, the thinner the lubricant becomes. How warm engine oil can get thus depends on the viscosity on the one hand – and on the driver’s driving behavior on the other.
The engine water temperature is around 85 degrees to 90 degrees Celsius. Nevertheless, drivers should avoid cold starts, because the engine oil warms up a little later: after about 10 minutes, the engine oil has also reached this temperature. The engine itself is at about 100 degrees Celsius during normal operation, which is why the viscosity of the engine oil is also indicated at this temperature by the SAE designation. However, the engine can also get as hot as 150 degrees under heavy load and a harder driving style – and the engine oil must of course be just as efficient here. Modern engine oils can usually cope with these different temperature ranges without any problems, because the additives added to synthetic oils additionally improve the load capacities of the lubricating film – nevertheless, too high speeds should be avoided when the engine is cold in order to give the engine oil time to warm up. This prevents wear.
Basically, the SAE viscosity rating of engine oil is one of the most important clues for checking how warm the engine oil can get and for which temperature ranges the product at hand is suitable. In addition, most modern car models have a water and oil thermometer that provides information about the current temperature. If the temperature is too high, significantly above 150 degrees Celsius, you should ask the manufacturer or seek advice from a workshop – often the engine is no longer cooled properly in these cases, in which case the breather or the coolant may need to be checked, as the oil film of the engine oil is often no longer completely tight at excessively high temperatures.