As far as I know, all new compressors can run any refrigerant. The only issue might be an older R-12 compressor seal not being compatible with R-134A, though I never read of that. I suggest looking at PAO 68 oil, which is fairly new. It works for any viscosity requirement and compatible with all refrigerants and former oils. It is supposed to stay put in the compressor better, which seems important for the Harrison R4. I used Duracool's version they term "Oil Chill" or such, along with their HC refrigerant, in several cars including my two 300D's - one w/ an R4 and one with a Sanden (Rollguy's brackets). If using a shop, R-12 is your best choice since most enforce a quasi-conspiracy against HC refrigerants.