Next time i change my oil i was thinkin about switching to Mobile 1 full synthetic and an AC Delco filter. I have been using Castrol GTX and fram filters up to now. My car has run on conventional oil for at least as long as i have owned it, and im pretty sure it used conventional befor that. My car is a 1997 vw passat VR6 and has 87000 miles on it and i was wondering if i would experience any problems with the switch(leaks, etc...)? Anyone here ever make the switch with a high mileage car like mine?