When do you wait to fill up your gas tank? Do you constantly keep it full, half empty, riding close to 'E'? One blogger writes about what she thinks the advantages and disadvantages are of different fuel levels.
Kristy Welsh writes:
There has recently been a lot of talk on how you can get better gas mileage by driving when your tank is half full to empty or making sure you fill up when your tank is half full. Which is correct – or does either method hold any water?
The fill ‘er up when it’s half full foks proclaim that if you leave the gas tank empty, the gas will be evaporating in the empty space of the tank. Gas tanks are designed to force out all those gas fumes from the tank into the atmosphere and this gas is wasted. Yes, it’s true, but how much gas are you actually losing? To tackle this one, I woke up the engineering part of my brain (I used to be one) and looked at a paper published by the Environmental Protection Agency and their analysis of gasoline storage tanks and the evaporation rates.
At 60 degrees Fahrenheit, a gallon of vehicular gasoline weighs about 6.15 pounds. In the above paper on page 87 (if you want to chew through it), they go over what the gasoline vapor losses are for large storage tanks. For a 8400 gallon tank the total loss is 48 lbs (or about 8 gallons) a year.
Read more: http://www.creditinfocenter.com/wordpress/2008/07/24/increase-mileage-gas-tank-full-or-half-empty/
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