I got the Shell ATF 134 MB 236.14 transmission fluid from Ryder fleet products (maybe ryderfleetproducts.com) for like $4.26 a quart plus $7.95 shipping on 9 quarts. Made it only like $5 something a quart.. still 236.14 and a lot cheaper than $15+ at MB dealer. I have not yet changed the fluid though. It was done about 40,000 miles and 2 years ago. It may not need to be done I just don't want any problems and thought it'd be a good idea. I also plan to change the motor oil and filter every 5,000 miles.