Miles Per Gallon Question

I’ve got a question for those of you that are interested in squeezing every last cent out of a gallon of gasoline. I’ve been hit by higher prices as well, but I’m by no means becoming fanatical about it (yet). I suppose it’s just depends on what get you all riled up. For me I’d rather cut expenses in a big bucket (like groceries) than I would worry about something that I can’t affect much. But that’s just me.

Let’s get back to the point though. Clearly the weight of your car affects your gas mileage, and I’ve read that 100 pounds can degrade your MPG by 2%. So my question is “How much would keeping your car’s gas tank 30% full (or less) affect your gas mileage?”

Let’s see what the math says. A gallon of gas weighs 6 pounds, and let’s assume that a typical gas tank holds 12 gallons. Therefore a gas tank that is one third full would be 6*8 = 48 pounds light. This should result in 1% increase in miles per gallon, or 0.25 more miles per gallon for a car that typically runs 25 miles/gallon. In other words it isn’t worth much… So much for that theory.

Image Credit: juniortrainor

Correction: An earlier version of this article had a few math issues, most notably that 1% of 25 mpg is .25 mpg, not 2.5mpg. I suppose that’s what I get for trying to do even simple math in my head late at night! Thanks to Mark for pointing out “The Relentless Rules of Humble Arithmetic”

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