So, what's everybody's opinion on mixing conventional and synthetic? I have often heard once you start using synthetic you shouldn't go back to conventional. It doesn't make sense to me. I think synthetic has a higher profit margin and the 'can't switch back' story is a sales gimmick....
...as far as my Valiant goes I change the filter but not the oil. Between the burning and leaking just 'topping it off' keeps it fresh.