You don't have to use R-134A. Indeed, it is being outlawed and no longer ships in new cars for several years. I use HC refrigerant (Duracool, Envirosafe is another). It works better than R-134A, indeed even slightly better than Freon (R-12). It is compatible with mineral oil, but I would still flush out the evaporator and install new "barrier" AC hoses (Viton lining). I use PAO 68 oil, which is compatible with all refrigerants and more efficient. Ignore the crazy claims that HC refrigerant can "explode". Those ranters know nothing about combustion. Millions of cars use it with no fire ever reported. All refrigerants burn, if not themselves, the oil which sprays out with them, and many form very toxic products when they burn. If you don't buy a MasterCool ferrule crimper, you can use Oeticker stepless ear clamps (ebay) or even the similar PEX crimps at Home Depot.
