Yes, if the compressor is removed, just dump the old oil out, but I think
most of these compressors are installed and pressurized. It is lots of
expense and work top reinstall a compressor. Cost about $1500 or more
(including a new compressor).

 I think the Sanden 508 takes 8 ounces of oil+ 1 ounce in the rear valve
plate area to lubricate them upon first start up. Most folks don't add this
additional ounce, but the vendor that supplies compressors to Bus Depot does
this.He takes the best care anywhere of his product and reputation. In the
super large system the the Vanagons have, one ounce extra is a good
safeguard that won't over charge the compressor or slug it.