There's a great post at The Oil Drum by Jeff Radtke that gives people a good way of evaluating the resource uses in their cars. Now you don't actually have to do this to figure out that light cars are better than heavy ones - the results aren't that difficult. But if you think it is fun to figure out smaller distinctions, it is worth doing.
This type of analysis is useful because it is easy to factor in conversion efficiencies and payload versus tare weight. Rather than use motor output power, one can use the thermal power theoretically available in the flowing fuel. EROI may be factored in…