Grab a diesel van or truck with a cap and convert it to bio-diesel. A buddy of mine and his friend did this and traveled down the East coast to Florida, then west across Route 10 to California, and then south into Mexico. They built bunks in the bed of the truck for four of them. They had one 55 gallon drum connected to the fuel line and a second to filter oil that they were able to collect. It sounds like it was a pain to be stopping at fast food joints left and right asking for their oil and getting rejected. But the cool thing is enough of them said yes that they never had to buy fuel! I probably wouldn't go this route b/c I'm not very mechanically inclined but I think the kits only cost $1,000, so if you're on a tight budget it could be worth it. Just my $0.02.