My reman R4 has been kicking a** with 134a. After all the money I spent to get the system going, R12 is waaay to expensive for me. The R4 has a 2 year warranty from advanced auto so if it dies ill just get another, Just make sure I don't let it clunk me in the head when installing lol. I know R12 would cool off the car faster but I am happy so far as long as its working. If it gives me any real trouble I will break down and buy some R12.