I have seen this go both ways. If the r-12 is available to you, it will be fine. The only thing that I have seen is the 134-a will dry out the oil on some occasions and the compressor will sieze up after only a shor time. I see more and more people recommend the 2 year drain and re-fill of the system of new 134 and oil.
1981 280GE SWB
ASE CERTIFIED MASTER AUTO TECHNICIAN
SERVICE MANAGER FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM