Originally Posted by harbor

In the never-ending quest to improve my manual transmission shifting, I put in some MB manual gearbox fluid spec 235.1 that I got from Rob@Needswings. This is the fluid that MB spec'd for the '03 SLK320 and the 2nd gen MB C class.
Note that our owner's manual specs a 236.2 fluid (which is ATF) or 5w20 motor oil (which is motor oil).
After trying syn motor oil and Amsoil synchromesh, this 235.1 fluid is by far the best I've come across. Shifts are not quite like butter, but close. I'll see how it behaves over time and in cold weather.
While I was at it, I also threw some Red Line 75w85 in the diffy.