Does anyone have any experience with adding PAG lubricating oil to a system that lost all its refrigerant? My system in a 2008 GM (R134A) was lost to the atmosphere from a leak at the high pressure connection to the evaporator. I plan to fix the leak, replace the accumulator and orifice tube, pull a vacuum and recharge. What about the lube? Any rule of thumb on how much to add? Thanks.