You are on your cell phone bragging to your doubter buddies that you are cruising down the road, your car fueled by a few handfuls of yellow and brown autumn leaves. But the car sputters and dies giving you only enough time to pull over tot he curb. You check the fuel hold. The leaves are atomized already. You wander about the ditch picking up old fast food cups and bags to stuff into the hold. This gets you another third mile and you are out of power again. This engine is burning materials way too fast and its so hot in the cab. You are sweating with the A C on and the windows rolled down. The under carriage of the car is too hot to touch. Looks like its going to need a lot more work. But you know you are on the right track.