Is their a drain plug to take out so I could remove the old oil from the compressor? Also if I go about removing the entire compressor from the car it looks like 6 bolts. Is their a trick/tip for removing them especially the lower one next to the thermostat housing.

Finally what would be a good oil for the change if I'm using r420a? The website says mineral oil that the original system used is fine, but it also it's compatible with any oil. Is one superior over another?

Looks like I'll be redoing this system again. New expansion valve and filter-dryer and system flush. Compressor turns free and smooth I just want to clean any debris out before reassembly. As you probly know it's a lot of work.

Thanks for any help.