Factory AC can work great with R-134A if you know a few secrets

You really don't need to drain all the oil, It does not mix with pag oil or R134a. It just goes and lays in low spots and corners in the condenser, so the pag oil flows through the system with the R134a. I don't like anything with propane in it for refrigerant just because there has been car explosions from leaking evaporators and people smoking. It has been documented and is a fact. The fact is anything can be combustible if the mixture is correct, that has been the argument for years. Propane is highly explosive and in a small concealed area inside a car, I would not want to be in when someone lights a cigarette.