Comment: Free space, free time, free maintenance, free components...

nuthin's free.

Cheaper, yes. I'm all for that.

Used to run around in a diesel truck that burned 'free' cooking oil as fuel.

-free after buying filters
-free after investing time to collect the oil
-free after devoting space in the garage to store the oil and filtering equipment
-free after buying viton hoses that wouldn't break down like natural rubber would have
-free after doing hours of research and adding my own experiences to www.biodiesel.infopop.cc

Free? Not exactly. Cheaper? Possibly - all things considered.