Can PAG and mineral coexist in old R12 system?

[Swedal]

I'm going to replace a condenser and drier on a Mazda MX6 1993 with R12 system. There is a sticker in german that system contains ozone harmful gas but on the other hand there is a R134 connector on the high side so I really don't know whats in the system and whats done with it. I have tired the system with a HC mix of 50% R290 propane and 50% R600a isobutane (sells as Hychill in austalia) and that works with both PAG and mineral. System cools well but I had to use more R600a because of high head pressure. After replacent of condenser and drier I will use 50/50 mix again and get some better performance.

Now to the question. I will need to add some oil. Can I use PAG46? I know the HC mix will work with both types of oil but what if there still is mineral oil in the system? Customer budget is very limited so I will not mess with a flush and oil change. Will PAG and mineral oil work together with HC?

[vintage air tech]

If the HC refrigerant is comparable to R134A, the mineral oil will not mix. the mineral oil is not soluble in R134a and will gum up. But there is very little information on these replacement refrigerants since they are recognized as a replacement for R12.
These refrigerants are neither R-12 or R134a Despite what you may have heard, there are no "drop in" replacements for R-12. Don't use refrigerants that make such claims. Some of these "snake oil" refrigerants are explosive and all will contaminate your system. Keep it simple and use materials recommended by the systems manufacturer.

[ice-n-tropics]

g'day mate,
PAG in R-12 system?
GM brochure GM-0011 indicates that removal of mineral oil during retrofit (mostly paraffinic in GM's case) is not recommended. Long story short, GM/USA avoids residual flush. OEMs are not all in agreement.
Mineral oil and R-134a are far apart on the polar compatible scale so oil coats the heat exchangers and results in a minor reduction in performance but no oil compatible problems with PAG per GM.
Residual R12 will cause copper plating. The mineral oil will retain absorbed R12 unless it is under vacuum for several hours or in a open system several days.
In the USA, farmer/ranchers sometimes use R600 with mineral oil because R12 is not available and the smell is obvious when a schrader is depressed, but it is dangerous, but they live with hay baler mobile campfires etc.

[Cusser]

GM brochure GM-0011 indicates that removal of mineral oil during retrofit (mostly paraffinic in GM's case) is not recommended.

Can you attach or scan or link such brochure, I'd like to see it.

Actually, I'm surprised that GM would even address such conversion to R134a, figured their official stance would be to keep it as it was from factory.