The big issues as I understand it with straight oil is the higher acidity, which will lead to pitting and accelerated etching. When you convert vegetable oil to biodiesel you're first de-watering it, then performing what's called "transesterfication" which removes the fats and adjusts the pH. Basically refining.

For the folk in the article they could basically run the engine on straight oil till replacment then just get another cheapie for replacement and they'd always be ahead in $$$. But getting a good system down for refining the vegetable oil to biodiesel and then establishing a collection technique and routine with your local restaurants is, in my opinion, the best way to go. That way you have less wear and compatibility issues, plus you could sell any excess fuel to a local co-op.

Lots of possibilities! Kinda makes you want to put a 4BD1TC in the VX.