http://www.hammerzone.com/archives/hvac/index.htm

And just to make it clear, I'm NOT recommending that you try these
techniques, just trying to point out that removing the oil and the task
is a considerable effort, and probably beyond the capabilities of most
homeowners even if they can discover the procedures and obtain the
equipment to do it safely and in compliance with local requirements.

Michael Thomas
Paragon Home Inspection, LLC
Chicago, IL
mdtATparagoninspectsDOTcom
847-475-5668