Yes, it makes a brown mud. The idea is to remove at least 80 percent of the
previous chemicals that were inside. In a vanagon this is about 15 ounces,
including  the compressor.

Some areas are very difficult to purge.Like the evaperator(2 ounces). So,
plan on leaving that oil inside the evaperator.  If   you drain the
compressor, you will get probably 7 or the 8 ounces. Be sure to replace the
o-ring on the compressor fill hole. Rinse it with mineral spirits? A new
dryer will get an ounce out. Flushing the condenser and hoses will get
about 4 ounces out.  5+7=12 ounces removed. 12 is what percentage of 15?