AC Conversion question

[TQ60]

We have a 1989 38 ft coach that has low R12 freon levels, it still has coolant so I doubt major leaks, just drift down form being years old.

We have upgrades other vehicles to R134 and they have been easy with the vehicle label indicating how much.

We will need to replace 2 dryers and clean out all of the old oil.

Amount of R134 is not an issue as the guages tell us, the problem is how much PAG oil do we use.

Are there are links or guidelines to calculate how much oil to add to a system?

One compressor, 2 dryers, 2 evaporators, one condenser and a whole bunch of line make it a difficult guess.

[RV Wizard]

I believe one bottle per compressor is the norm. You can call an auto parts store that sell compressors and ask them; they should know from the mechanics that frequent them.