When I bought the truck, the AC clutch was out and the system had slowly leaked down to zero psi. I replaced the compressor, a line, vacuumed it down, charged it up. Worked great for around a year. I believe the compressor had oil in it already. Now I am having to replace the condenser due to a leak, as well as the drier (easy to get to so i'm doing it). I have no idea if I should add additional oil before vacuuming it down and firing it back up. My guess is that a fair amount of oil was lost when removing the condenser, but I don't know how much. ???