Larry is right. If you're staying with R-12, a CFC bases refrigerant, then the only correct oil type is mineral. If you're doing a R-12 to R-134A conversion, then there are two options. Either a POE or a PAG type oil is compatable with the HFC based refrigerant of R-134A.
The important point is if you convert to R-134A and continue to use the mineral oil you will have problems. The mineral oil reacts to the HFC based R-134A and creats a gel type substance. This gel will, at the minimum, coat the inside walls of your evap coil reducing heat transfer. But most cases it gums up so bad it clogges the expansion valve.