The Brazilian tree Copaifera langsdorfii (aka the diesel tree or kerosene tree) produces a natural diesel fuel that requires very little filtering (one pass through a coffee filter) before it's ready for use. Just kidding about the coffee filter thing, I don't know what it takes. You stab the tree and presto, delicious, natural diesel. Unfortunately the fuel only has a shelf-life of 3 months. I was still excited at this point, until I started doing a little further research (being the intrepid reporter than I am) and found a source (wikipedia) that states "despite its vigorous production of oil the tree does not grow well outside of the tropics and does not show promise as a reliable source of biodiesel." So yeah, shit. But who knows, maybe with a little genetic modification we can have them walking around and talking like the Ents in Lord Of The Rings. Then we won't need cars, we'll just ride those leafy bastards.
Gasoline Grows On Trees [gizmodo]
Thanks to Bigjerm, who doesn't need gas to run because he's a solar powered sex machine, for the tip