I'll second that criticism of the Mercedes, at least as it applies to my 3 w124's. I love/loved the cars but the A/C is going to go and it ain't pretty. Changing to a different coolant is a bad idea (yes, I'm a veteran of that foolishness) unless you (or your tech) is scrupulous about seals. The controller will self-destruct eventually.

Larry Bible wrote a lot about Mercedes AC that I found really useful after I screwed-up everything. Wish I had known about Mercedesshop.com BEFORE I bought my first Benz.