PAG 46 for GM/Harrison Compressors & R12?
 

I've read of the virtues of PAG 46 oil for R12 systems. Is anyone using it for the GM/Harrison compressors? (1985 300TD). Most sources say use mineral oil.

GM compressors require PAG 150

GM/R4 from my info need 500-525 visc mineral oil if using R12 refrigerant. The Pag and Ester oils are mainly for R134A refrigerant. Alot of people use the pag/ester oil in case of converting.

I am using R12 and went with BVA napthetic mineral oil 4 (325 visc). I had used Castrol 525 mineral oil before.

I've read conflicting information about oils best for GM R4's with R-12.
Some say PAG 150 is compatible & better, and others say stick with Mineral oil.
Does anyone using the PAG 150 for this application have some longevity figures?