It may work fine, but why take a chance? R12 is really as cheap as R134 in the grand scheme of things. Ask yourself this, If the big auto companies worldwide (GM, Ford, Chrysler, Honda, Toyota, Nissan, Kia.....) and all the truck guys (Peterbilt, Kenworth, Mack, Navistar, Freightliner, Western Star....)could use these replacements don't you think they would do it to save money? I've said it before and I'll say it again-the only thing I would ever consider using as an automotive refrigerant is R12 or R134. Neither of these is flammable.