No need to go to synthetic ATF on a 500E, esp. if you diligently change out ATF & filter every 30K miles, 15K (fluid only) for city or towing service.

If you want better shifting try either SWEPCO's 714 20wt. or Schaeffer's synthetic-blend ATF.

The Porsche 928 club-races swear that the SWEPCO ATF really makes the MB-tranny's (500E & 928-auto share the same tranny) much better. I've switched over to SWEPCO, and have to agree, especially since I've previously used Mobil 1 Synthetic ATF for 60K miles.

:-) neil
1988 360TE AMG (Swepco ATF)
1993 500E (Swepco ATF)