My car currently has whale oil in the transaxle. I am told that this oil was originally used by Ferrari and that there is no need to change the transaxle oil yearly. In fact, I was told that the oil could stay in there for many years since it is a "closed system". My question is can the transaxle oil remain unchanged for years without problems, or should I change it every year? If I need to change it, what is the recommended oil? Should I replace it with more whale oil, or use an Agip product? Thanks. Ken P.S. Where does one buy whale oil?