It's not quite as simple as it looks.
Friend of mine is a sound tech for Melisa Ethridge, she insisted all of the tour busses run on bio-diesel.
Bus drivers balked at first, and for good reason. There was nothing but problem with the engines initialy. Gaskets, seals, fuel lines, etc.. were falling apart.
After some mechanical fixes and a few oil changes, they ran fine. The drivers ended up really liking the change.
Not saying it isn't a good option eventually, just saying it's not a matter of a few quick turns of the wrench.
Someone in my area runs a early Bronco off of a 4 cylinder bio-diesel, rock crawler guy, says it kicks ass.