by using ATF, Canola Oil or BioDiesel. My thought would be Marvel Mystery Oil because it is advertised as a top end lubricant.
Any of these would probably (maybe) cause coking. I do particially agree that ATF isn't the best option as it has alot of other chemicals in it.
Some guys even pour there drain oil into the diesel fuel.
2 stroke oil has been recommended. Wal*Mart has it for about $7 per gallon. I am also running Non-Detergent 30W at about 1 qt per 10 gallons of fuel.
Tom
...where this was discussed:
http://www.acmoc.org/ACMOC_BB/showthread.php?t=3356
CS