http://www.machinerylubrication.com/article_detail.asp?...ookgroup=LubricationPAG has a very high viscosity index so it is important that you get the correct viscosity at operating temperature, if the OEM recommends a viscosity at 100 degrees F for a mineral oil with a VI of 95, you will have to calculate the viscosity at operating temperature, then use a similar viscosity PAG at that temperature.
http://www.eskoindustries.com/viscadv.php?Deg=C&Temp1=4...mp=60&Calc=CalculateI am considering changing the oil in our screw air compressors from diester to PAG. The OEM recommends a minimum discharge temperature of 180 F, I assume this is to keep the water levels below 500 ppm (0.05%), If I switch to PAG, I am wondering if I can lower the discharge temperature to get longer oil life (reduce oxidation), which will raise the water content (because water soluable types of PAGs can handle up to 0.7% water)