I just replaced the ATF and differential oil in both my '91 300E (165k) and '95 E320 wagon (75k) with Synthetic Mobile 1. Wow what a difference! Both cars definitely have improved in shifting. The 300E I was wondering whether a rebuild was around the corner. Very noticeable diffrence in shift points, especially in the E320.

I changed the trans filter in both at the same time. The hardest part was finding a 14mm allen socket for the differential fill and drain.