Well, I got about 400 miles until my next 3,000 mile service. So, I have always used Mobile 1 Synthetic in all my diesel trucks and in several Gasoline powered cars. (Unless special oil was required and recommended by the auto manufacturer). I have heard that the currently produced Mobile 1 Synthetic is not really synthetic. I am considering switching to Amsoil. Anyone have any comments? I am thinking of ditching Mobile 1 Synthetic all together. For my diesel and gasoline vehicles, I might bring in some lubricants from Ural Lubricants in Germany. Redline and Royal Purple I hear are more or less the competition for Amsoil. Agip has a very nice product that works well. A couple auto makers specify it exclusively and I have had good sucess with it. So many choices! Thanks for any advise.