Calculate your true Miles Per Gallon

Obviously a slow news week at the Business desk of the Washington Post. This Sunday saw them devote two thirds of the business section front page, and a further half page on page 2 to “Adventures in Hypermiling“. The article was another example of a non-story where a journalist was shown a scan gauge that calculated a real time, and short term average miles per gallon figure and drove their car around seeing how they performed against a “hypermiler” (the answer was, about the same). The scan gadget used in the article had the same functionality as found on most modern cars with trip computers, and isn’t new or exciting nor does it give you a truly accurate figure. So in the interest of spreading knowledge may I present…

Calculating you miles per gallon figure

  1. Start with a full tank of gas, so begin next time you’ve filled up at the gas station.
  2. Before starting your engine at the gas station reset the odometer in your car to zero. On older cars you just need to push the button next to the lower display of miles, on newer cars you might need to figure out how to reset the digital trip odometer.
  3. Drive you car. Drive normally, just don’t mess with the odometer!
  4. Next time you go to fill up with gas, get a receipt. The newer pumps give you a great receipt which tells you not just what you paid, but also how much gas was pumped in gallons.
  5. Now, before resetting the odometer, take a note of the miles covered. Divide the miles covered by the amount of gas you just pumped into your car (this is the amount of gas consumed since the last fill up, and therefore the amount of gas used to drive the distance covered).
  6. The figure you get when you divide “Odometer Miles Traveled” by “Gallons of gas to refill tank” is your true, Combined Miles Per Gallon.
  7. Return to step #1 and do it all again, try using the AC less, or not accelerating as hard, and see how it really impacts your MPG. It is different for everyone and now you have the data that relates to you, you can decide what you want to do to improve your mileage.

Note, the figure calculated is your “real” miles per gallon, and not the “city” or “highway” average that are posted in car dealerships. These figures are used in advertising because they look good, but they are only a guideline since you never drive at exactly 50mph anywhere. You have to slow down or speed up sometime, even if it is just when you start and finish the journey!

There, so now you can calculate your MPG figure, without any fancy gadgets or taking your shoes off. Not only do you know your MPG, but if you track it regularly you’ll be able to spot fluctuations that affect the economy of your vehicle, and can help you spot maintenance issues before they become serious problems.

Oh, and wear sensible shoes when driving. The Washington Post article noted that the hypermiler drove without shoes on because it:

allows him to better feel how much pressure he’s applying to the accelerator

Now when I was taught to drive, back in England in the ’90s, I was told to wear sensible shoes with a thin but firm sole. The reason was you need to feel the pedal, but you also need to be able to apply full pressure on the brake with your right foot, and an unprotected foot could flinch on a hard pedal and not apply full braking in an emergency situation. If you wear sensible shoes or sneakers you should be able to feel the throttle just fine (high heels and huge waffle soles do not cut it) and you’ll be safer in an emergency than if you drive in bare feet or socks.

Okay, so ends the first lesson.

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One comment

  1. Pingback: Review: Toyota Prius « BardsWorld

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