That is quite an interesting idea. Like you say it wouldn't prevent a theft but would rather help put it in the shortly ditched catagory as many are. It's good to know it's not the gas you were trying to protect, I wondered where you lived so as not to go there.

My cap is one of the more snug (of many) I have used, appearantly making a strong seal. Which would make me guess that a similar cap that created a similar tight seal would work.

I'm sure you've also figured out that to best impliment this thief foiler you would never want more than a gallon or two of fuel in your car.

__________________
Delsman
92' 400E, 107k
BMW 535i, 165k