i found that my new to me (56,000KM) 1992 300 SEL shifted a lot nicer and drove a lot smoother with 5w30 synthetic and synthetic ATF for the transmission (with filter kit) - i hate to plug any oil company (Lord knows they dont need it) but I found that Mobile 1 synthetic blends work great in my cars. The synthetic ATF really made a huge difference in the shifts - i would highly recommend that. And i second Xsbank - get the owner to make a windsheild claim. If you are not mechanically inclined I would recommend a CAA inspection or equivilant (AAA in the United states i do think...) It's roughly $100 and they take off the tires and give you rotor measurments, pads, tire tread depth, front end inspection etc... I think my report said it was something like 150 point inspection... it's well worth it if you are serious about buying any car