I,ve always had MB dealer change my oil, 1994 S320 gas powered, now turned 396,000km. The several area dealears hear use 15w40 HDX Quaker state oil in these cars. Relocation has made getting to a dealer a time hassle. I'd like to start doing my own oil changes but find the 15w40 HDX isn't that readily available. From what I understand this is an oil designed for use in Diesel engines. Will going to a normal 10w30 Quaker State do any harm. Any noligable opinions/experiences.