My 85 280SL Euro AC was converted to Freeze12 a few years back ( I had sold the car to a guy whose wife didn't like it so I bought it back after a year) I don't know why he converted it to Freeze12 and not R134 but he did. Freeze12 is 80% R-134 and 20% HCFC-142b. Shops don't want to evacuate the Freeze12 because they say it may damage their evacuator. My question is: can I or my shop add R-134 or possibly R-12 to the system to top it off? The only shop here that uses Freeze12 is very expensive and always booked so I would like the option to top off with R-134 orR-12 if possible without screwing up my system.Thanks....Desert