Jet engine oil is a one-way trip, as it's consumed like the oil in a 2-cycle. The oil consumption is slow, but it never returns to the reservior. It leaks out into the air/fuel stream, and is consumed in the burner section.

There's nothing wrong with lubricating an engine with vegetable oil with a bunch of additives. At least we don't have to dig it up from way underground, just plant a crop and process it appropriately.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!