Do You Check Your Car's Gas Mileage?

| 9/15/2009 10:43:00 AM

How long has it been since you last checked the real-world gas mileage of your car? Have you ever done it?

It can be all too easy to assume your car gets 30-something mpg — or whatever the sticker said when you bought the car — and never realize that its actual gas mileage has declined over the years and now is far off what you expect. But it's important to keep tabs on your car or truck's mpg.

First and foremost, "knowing is half the battle," as they used to say in the old G.I. Joe cartoon PSAs from my childhood. In other words, the first step to increasing your car's gas mileage (and saving money) is to know what it actually gets. Also, unless you're lucky enough to have a real-time mpg display in your car, there's no better way to better understand how driving habits influence gas mileage than to check the numbers. As in, on this tank I ran the air conditioning more than usual (you would see the mpg decline), or on this tank I drove the speed limit to work rather than speeding to make up lost time (you would see improved mpg). Last but not least, regularly checking your vehicle's mpg can spot maintenance issues before they become leave-you-stranded and wicked-expensive problems.

If you're a gas mileage geek like me, you'll calculate your car's mpg after every fill up. But even just checking mpg once a month or so will give you real numbers that will make it easy to adjust your driving habits so you save gas and money. Think of it as a personal challenge and you'll find it easier to get excited about the math — can you beat last month's personal best of 36 mpg? Can you beat the official EPA fuel economy estimate for your car?

And, to top it all off, you'll probably be surprised how easy it is to calculate gas mileage. Even a mathematically disinclined journalist like myself can do it. All it takes are two numbers and simple division. How to Calculate Gas Mileage will walk you through the steps.

For what it's worth, here's my system. I write down the number of miles on my trip meter on the credit card receipt from the gas station, which lists the number of gallons I bought. I also write down the car's overall mileage, just to help me track the car's mpg over time. I then plug all those numbers into a super-simple Excel spreadsheet, which does the simple division for me and automatically fills in the mpg for each tank. I can then track the car's mpg over time and see how it changes with the seasons, my driving habits, as I put off maintenance, after I got new tires, etc.

Greg K
1/13/2010 7:00:17 AM

I use

9/22/2009 1:59:14 PM

Indeed - gas mileage certainly becomes important during not only recessions, but also with the rising cost of gasoline. We're almost back to $3 a gallon, and it's likely to hit $4 again, most likely by next summer. Tires are a vital component that people often neglect. The closer your tires are to their correct psi the better off your gas consumption will be, and the sooner you replace tires that are approaching the end of their life, the better for it as well. The gentleman above is well to be concerned with ethanol. Most engines are fine with a 10% mixture. The thing about ethanol (ethanol is also known as alcohol - as in the kind that you drink - this driving thing is cutting into our booze supplies!) has a higher octane than gasoline, but a lower energy potential per unit. However, this can be overcome by simply increasing the compression - supercharged cars running on ethanol fuel achieve similar mileage to stock gas engines. The other consequence of ethanol fuels are the impact on food crops. Most ethanol crops are food crops. Grains, wheat, barley, and corn are the staple crops of ethanol production. You can take it with a slight grain of salt, however, in that only 20% of all corn produced is usable for human consumption. (Most is used for cattle feed.) There is a developing method for deriving ethanol from algae without harvesting the algae themselves that yields far higher amounts than any food crops. The effect of ethanol on food supplies...could be troubling, but it would likely affect exports more than domestic. The horrible effect that no one wants to contemplate is that grains that are well used to make ethanol for cars are the same that make ethanol for drinking...and we all suffer enough as it is, without them pricing beer out of reach. (That is an insult the people of the world are NOT prepared to tolerate.) There's also talk of using blue agave for ethanol fuel, which is the fabled plant used in making tequila. (Perha

9/21/2009 1:24:41 PM

I travel all over Northen California. I travel 126 miles a day on average.That is freeway and city driving in San Francisco. I purchased a 2008 Yaris hatch back stick. I have owned the car for more than a year,here is what I get at 60 mph or slower I get 40.8 at 70+mph I get 37.89. The car is rated at 35mpg. I think it's a joke that the American car compaines have to work real hard to get to 30 average. They buy second geeration hybrid from Toyota,cars from Korea,or use technology created in europe to shut off cylinders. Mean while VW has a 230mpg car that runs on bio diesel. GM should have improved the battery EV1 and we all would be head of the curve. Lets go to alge fuel with hybrid. How about the air car, or the one in Japan that runs on a liter of water

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