Not sure....I wonder too when I'm not worring about work or something.
Personally, I'd like to see more diesels on the road.
Diesel technology a improved
greatly in the last couple decades and is continuing to improve at the same rate. They are not the slow, smokey, smelly, and loud things they used to be.
I drive a Jetta TDi wagon, great car. I have yet to run biodiesel in it but the prospect of making my own biodiesel is something I find very attractive.
I know people who've done this. It is a HUGE pain in the rear. I'd try LPG or Propane.