In my case the answer was "No, you can't". After passing out all the spare gas we had to help stranded Rita evacuees we encountered a car with four ancient ladies in it. The youngest was in her late seventies and they were out of gas. I decided between our Honda Pilot and RAV4, both with filled tanks, I could spare them the gasoline I was keeping aside for my unleaded gas Coleman stove. I thought if I needed the stove to cook I could just siphon some gas from one of the SUV's. Well, later when I went to siphon the gas I discovered I couldn't. They both have blocks on the gas tanks to prevent this. D'oh!! I should have know this.

-Blast