Recently encountered another old R12 two door box running MP39 that had a compressor less than two years old with a failed compressor.
Granted restaurant equipment can take a severe beating. God knows this one did. Close to a fryer and the kitchen help doesn't monitor box temps.
But it seems that the original R12 systems were able to handle more adverse conditions and survive.
MP39 runs at a higher pressure than R12. The shell temps on some of these compressors run hotter. The amperage is higher.
My supplier has a good price on a mineral oil Tecumseh. Probably because they're not shipping these anymore.
Since I carry POE oil on the truck I'm seriously considering as a test to convert this one to 139. Just measure out the mineral oil and add back POE.
I recently inherited an old grocery store that was all old equipment that was entirely 404 and 139. And I have to admit I like seeing that 139 pressure on the gauge. And that equipment was old and surviving well.
You input is greatly appreciated.