As far as synthetic is concerned, if your car has more than 20,000 miles
then I would hesitate in changing oils. The more people I ask, the more I
hear the same response. "Sythetic is the ideal oil, but you should use
standard oil for the first 10,000 miles in order for everything to
"bed-in". There is a big debate out there about gasket leaks after
introducing synthetic oil to a high mileage car.
When I (not if) I get my ZF transmission rebuilt, I will run Redline
Synthetic from the start.