Saving gasoline

http://www.msnbc.msn.com/id/12502313/
http://www.msnbc.msn.com/id/12517107/

I have found a way to lower gas milage that I haven't seen elsewhere, at least not the specifics. Articles on reducing gas milage do recommend avoiding carrying heavy items around in the car on a continuing basis. But nobody else points out that gasoline is heavy. If you've ever run out of gas on the highway and had to carry a can of gas back to your car, you already know this!
Several years ago, I kept track of my gas milage when I filled up the tank every time I got gas, and then when I filled up about half-way each time. I got a noticable improvement when I only filled up half way. This should be no surprise, because the heavier your car, the more energy, i.e. gas, it takes to move it. Now I can understand that people might not have thought about it. Who has time to think about every conceivable aspect of the universe? But what I don't understand is people who say it can't be so. It's just simple physics and common sense. If someone doesn't believe it, it's easy to check it out.