I may pressume that oil could be added without discharging your refrigirants. Hindi ko na kasi maalala kung ano ginawa nun, :P

Iba naman ang linya ng oil sa compressors and yung line ng R134a. Sandali lang magpakarga ng oil sa compressors, 20 minutes would be enough. Para ka rin nag-change oil ng makina, remove the old oil then add new oils in.