[cripplecreek]

If I had a grant, I could flesh this out some more ...

Maybe your study can explain this phenomenon. When my wife says the car needs gas, she means there's enough to get 98% of the way to the gas station.

[RadioAstronomer]

I personally keep my car above 9/10ths full. You never know when you may need it and cannot get it or don't have the time to get it. So I fill up on the way home every time from work.

Also it is cheaper on the wallet. As the price of gas keeps going up, the stuff in my tank pretty much always cost less that the current prices.