I had my mechanic convert the system in my 300E to r134a and I couldn't be happier. Since the conversion I have spent a year in Austin and two in Houston and the car cools as well as it did before the conversion (I would even say it cools as well as when we picked the car up in 94.) The reason I changed is there was a small refrigerant leak in the system that would necessitate a recharge at the start of summer. I decided it was easier just to recharge the system once a year and with r134, cheaper (Altough refrigerant prices have shot through the roof recently?????)