I've read through all the old posts about synthetic oils. For the most part people seem to like them. It's about time for an oil change and I was wondering what weight should I use? I live in seattle. If a leak did spring up, could I go back to the old oil and get rid of the leak? Is it possible to do any damage switching the oils like this? I have a 1990 300te with 118,000 miles. Thanks for you help


Ranger