My 1985 190d has a working a/c system, at least in my cool northern climate.
But there is always a drip or two of oil around the compressor, and I know it isnt from the engine, which is nice and dry.

So I was wondering what sort of preventative maint might be practical in such a unit. Its oem Im sure, and as noted, puts out cold air when asked to. It hasnt had a touch up recharge in four years. I hate to say it out loud, but the last time I did it, I used one can of freeze-12 and no oil.