If i could know for a fact that i would be able to secure a reliable cheap/free supply of cooking oil, this would be pretty tempting given that we own two diesel vehicles (both VW hatchbacks that get 40+ MPG). If i remember our budget, this is going for roughly what we spend in 1 year on fuel. So given that i'd still have to buy chemicals, the inevitable maintenance on the machine itself, and the work/risk/hassle of the actual process... i think it's still a little ways away for us. But tempting. And i like that it is getting closer to practicality.