I don't have owners manual for my car, and I am wondering what the proper engine oil for my 1987 Fiat X/19 bertone needs. Also I was told by a few people, not here on XWEB but around my town. If a car was ran using regular oil, then you should stay with that type of oil, and do not change to synthetic which could damage the engine. Synthetic is way better but I don't want to risk if this is true.