Mobil 1 is a full synthetic oil and is "endorsed" by MB. I use Mobil 1 in my Chevy van and Mercedes. I still use dyno oil in the Honda. All of my engines run like new. I have noticed that the engines which use Mobil 1 seem to run smoother. I havn't checked myself, but I have heard that synthetic oil can improve your gas milage.
David C Klasse,
The synthetic oils that I have seen state that they are fully compatable with non-synthetic oil. You shouldn't have any problems going back and forth as long as you change it often.
1998 Mercedes E320, 200K Miles
2001 Acura 3.2TL, 178K Miles
1992 Chevy Astro, 205K Miles