LOL,
although sometimes we go over the top with oil e.g. we always go for the highest spec. My last car needed gl4 gearbox oil. Some people would use elf oem stuff and a lot would use other stuff. But the people using the other stuff used gl5 thinking it was better but the gl5 apparently didn't like being used where gl4 was needed and could eat up some components. I don't know if this was true. I don't use OEM engine oil but you do need the match the engine spec to the oil. E.g. BMW does need ll-01 or LL-04 etc etc.