What oil to use with R134?

[RiverRat]

I have motorcraft PAG oil in my system now but was looking to add a few oz since I have done some R&R.

I went to the local parts store and they have different viscosity PAG oil and Ester (sp). I don't want to contaminate the system so which is the way to go?

 

[Glacier991]

If you had a converted system with ester, I'd say stay with ester. PAG is NOT compatible with anything but PAG ( or so goes the conventional wisdom), so STAY with PAG ! ( and for the naysayers some mfgr's say keep separate gauge sets for PAG and POE oils!)

I add one thought.... there is a school of thought that says overcharging with oil may kill as many compressors as undercharging! (still trying to figure out why, but assume is has to do with compressibility). Ah for the old days when compressors had their own oil sumps, and refrigerant didn't have to act like gasoline in a 2 cycle engine....

Happy Exploring..

Chris