My friend Colin Hefferon, who, like me, test drives new vehicles for About Cars is, in his day job, the ultimate expert on biodiesel fuel. So this week he hustled over to the 2006 National Biodiesel Conference in San Diego after trying the new Dodge Caliber at a Phoenix press launch.

I'm curious to hear his reaction to the "Willie Willys" pickup (shown here) which, reports Autoblog, was presented at the conference to singer and biodiesel advocate Willie Nelson. A recreation of the 1941 Willys, it is powered by a 6.5-litre, twin-turbo diesel engine generating 350 horsepower. Surprisingly, it has spark plugs, which the designers state will help reduce particulate emissions. The truck is expected to average 38 mpg.

If that last claim is true, it makes it difficult for me to suggest that, as an environmental statement, the Willie Willis ought to have been driven by a much smaller diesel, perhaps getting as much as 50 mpg. But I will, anyway, because I admire those original Willys autos, with their small, economical engines.