a guy in seattle was parked by the beach (west seattle) with a truck he claimed ran on wood instead of gas. i thought it was bullshit. i looked the system over and the engine over and could not find a fuel source and he started it and showed me how it worked.
i had to look it up on the web before i could begin to believe it. aparently, it was common during WWII
http://www.answers.com/topic/wood-gas
"Wood gas can be used to power cars with ordinary internal combustion engines if a wood gasifier is attached. This was quite popular during World War II in several European countries because the armies active in the war had all available oil. In more recent times, wood gas has been suggested as a clean and efficient method to heat and cook in developing countries, or even to produce electricity when combined with a gas turbine or internal combustion engine. Compared to the WWII technology, gasifiers have become less dependent on constant attention due to the use of sophisticated electronic control systems, but it remains difficult to get clean gas from them."