It seems lots of things work (for a while). There are a number of problems with what you have done but enforcement is weak so you probably won't get caught.

First problem is that the EPA absolutely does not allow blending refrigerants on your own. This means you must have all the old refrigerant out. Next you absolutely are required to put refrigerant specific fittings and labels any time you alter a system.

And just for fun any reputable shop will not touch it anymore as there are no mechanisms for recycling blends which is what you have. Was it Will Rodgers or P.T. Barnum who talked about suckers. Why didn't you just dump in some 134a its cheap. What you put in is 80% 134a and 20% HFC142b. Do you suppose that 20% 142b is going to allow the mineral oil to do its job of lubricating.

For your sake and some poor shop owners, I hope it manages to last till the car is gone. I would pity the guy who has to repair it next.

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Steve Brotherton
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician