In the 2003 Jetta TDI that I traded in with 380,000 miles on a new on in Nov 2012, I used nothing but Amsoil Series 3000 5W-30 diesel oil every 10,000 miles, with a couple of 20,000 mile oil changes (with oil sampling to back it up). I did my first oil change at 5,000 miles, considered that to...