When buying oil, you must follow two basic rules.
Oil quality: Mercedes has its own lubricants research laboratory, where all brands of oils sold are regularly tested. If the test sample meets all the requirements, it is included in the list of acceptable for use. This list is quite long, for information, please contact the company's service center. There are several systems for designating oil quality. Along with the common designation of the American Petroleum Institute (API) there is also a classification of the Association of European Automobile Manufacturers (ACEA), US military (MIL) and some others.
For reference: all motor oils specified in prescription sheets No. 226.0 can be used; 226.1; 227.0; 227.1; 228.0 and 228.1.
It depends on the viscosity of the oil whether the starter will be able to start a cold engine, whether all lubrication points will be provided with oil immediately after the start, how well the oil film is preserved at high temperatures and speeds. American Association of Automotive Engineers (SAE) introduced the following classification of oil by viscosity: from low-viscosity winter SAE 5W, 10W, 15W, then intermediate SAE 20W / 20 to viscous summer oil SAE 30, 40 and 50. Thus, SAE 15W50 engine oil at a temperature of -15°C corresponds to a viscosity class of 15W, and at a temperature of 100°C -class 50W. A characteristic feature of all-season oils is the decrease in their resistance to high temperatures over time. For this reason, multigrade oils of SAE 10W30 and 5W20 classes are not recommended for use in the warm season.
Special oils are designed for diesel engines. It is also necessary to adhere to brand recommendations.