I wouldnt bite again on the sanden solution. I have it in my car and my daughter has the factory R4. I have R12 in my Sanden and she is using 134. I cant see any functional performance difference between them. Then some folks will play the reliability card implying that R4 is unreliable. Uh huh. Her R4 is the one that was in the car when it was parked about 14 years ago, sat for over 10 years before she revived it. Still works. I am on my second Sanden in 3 years.

This isnt conclusive data, but it is my experience with both systems. I could have bought 4-5 R4s for what I've spent on the Sanden solution.