Muttley

The normal acceptable quoted leak rate is between 25 - 100 Gram/year (1 - 4 oz). My 400 has between 1 - 1.4 Kg of R12 (Freon). As for the changing of gas in the system mine now runs on HC's. They seem to work well and don't need major conversions or oil changes. They are a lot better for the enviroment ( R134a is about 70 times worse for global worming) and apply less load to the compressor. The change is in it's infancy on my car but I'll try to keep you posted as to what happens.