The reason for the N number requirement according to the fuel jockey is that some people have been using Avgas in their hot rods and the FED wants to make sure road use taxes are paid if the fuel is used on the highway... I'm all for preventing terrorism but downeast is correct I'm not going to register my saws as aircraft so I can buy a little gas... ;-) A friend of mine buys his for antique tractor pulls to get a little more umph from his 50 horse farmall.. Pulls his tractor right on the tarmac (actually one runway airport) and gasses up. You won't see that at O'Hare Intl.!