What Otto said about pressure building up in the tank. Our old trucks are not a modern design to capture fuel vapors and leaks. I bought a new Spectra Premium (original style) tank, filler hoses and gas cap. Filled it up with non-Ethanol. Everything was running great. A few days later I pulled it out of the garage and parked it in the driveway. The sun came up, the cab got hot inside, and it leaked gas at the cap. Thank goodness I had parked it on a slight slope. The gas didn't drip down the side of the cab and ruin the paint. You have to remember not to fill the tank too full. Many gas stations have an underground tank, and the gas is at ground temperature. Gas expands as it warms up.
