If you are changing Mobil 1 at 3K miles, you are wasting your money. IIRC, a R&T technical article stated that BMW determined that synthetic oils can go over 10K drain interval without any problems. I change mine about every 6 to 7K, along with a Motorcraft filter. On the flip side, I know many people who have cars still going strong with over 200K and have NEVER used synthetic oil, only conventional!
