If you have an old worn out motor or one that has not been well maintained.. DON'T try and switch to synthetic. Otherwise:
Oone of my customers has a well maintained GEO that had 112,000 miles on it and made the switch to 5W-30.. It runs just fine, and now has 169,000 miles on it..
This is with AMSOIL.
My Cougar has 86,000 miles on it and runs like a champ without oil loss on 0W-30.. and a single oil change per year.
My SLK uses AMSOIL 5W-40 European and the Honda Odyssey is also on AMSOIL 0W-30 and getting almost 30 mpg on the highway..
PM me if you want any advice on your car..
