My 83 wagon has held up extremely well considering Minnesota winters and road salt, but it is getting a few spots of surface rust, especially on the tailgate. I had the car rustproofed when I bought it and I think that helped. I just completed a major project, replacing the hydraulic lines running from the pump and reservoir to the level controller. The original lines had corroded over the rear axle from salt and crud. The MB dealer couldn't locate the factory replacement lines, so we ended up fabricating them from steel fuel line and reusing the original fittings.
I get a lot of compliments on this car even though it is now my winter car, as I drive my 87 300TD wagon in the summer(Southern car that has never been exposed to winter or road salt) and only 81K miles.
I also haul my dogs around, 3 of them, and I tow my snowmobiles!

__________________
83 300TD wagon
87 300TD wagon
89 BMW 325IX