Bought a couple of R134 retro kits. I converted my wife's VW 2 weeks ago - added the ester oil and R134. It works great. Read a thread on this forum where a fellow had a compressor grinding inside and has a major repair on his hands after retro R134 kit was installed. The manufacturer of the retro kit states that as long as you are recharging a closed system - the old oil will flow to the lowest place and it won't do any good and it won't do any harm - it will just be there to be removed when service is needed in the future. The new ester oil will coat all rubber parts and make them usable with the r-12 rubber components and R-134. I know the kit worked good on my wife's VW - but did the retro kit cause the other fellow's compresser to break apart inside or was it coincidence?? Has anyone done this kind of inexpensive R134 retro on a Mercedes with success - or should I not attempt it on my "baby"?