Do You Check Your Car's Gas Mileage?

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

Tags: question to readers, mpg, gas mileage,

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

9/19/2009 6:39:20 PM

I check mine every time I fill up.... I do share my car with my hubby somedays, and if he fills it up he checks (if he remembers). My father instilled a strong will to car for myself and my things at a young age, so it was a natural extension to me.

rick b.
9/19/2009 12:54:33 PM

I also bought a Scangauge for my 02 Silverado,mainly to monitor instantly the effect of mpg increasing devices that I've installed,such as the Vortex device(waste of money),additives,etc..By far,the best increase has come from hydrogen boosters,which I build myself.With this 3rd generation unit,which would be better suited to a 4 or 6 cylinder engine,I still see 3-5 mpg increases,with no other engine modifications.This is accomplished(simply put),by boiling water.At the risk of sounding a bit crazy,I'm also looking into using a small steam engine to accelerate a vehicle from 0 to 30 or so mph,where most fuel is consumed.If some analysts are correct in $6+ per gallon in the near future,we working stiffs are going to need an edge.Feel free to contact me with ideas or

9/19/2009 2:00:23 AM

I keep on eye my gas mileage at every fillup. It is hard to get accurate for every tankful. Here in Oregon there is no self-serve. Gas attendants in a hurry often don't take time to really top it up. My '88 Mercury Marquis has the 5.0L V8, and fuel injection. It gives me around 20 mpg local, and as much as 25 on trips. It prefers premium. Gives a big loss in performance and economy if I try running regular grade gas. I hated the 10% ethanol fuel when it was first mandated here in Oregon, but the car seemed to eventually adjust to it and does okay on it now. With 170,000 miles on it, the big old Mercury runs well. I had the AC converted to the modern refrigerant and it blows cold and gets a lot of use in summer. It probably costs me about 2 mpg to run that. Keep your rig serviced regularly and drive it easy like an old man. It will last longer and give you better fuel economy no matter what you drive.

9/18/2009 10:42:57 PM

I've checked my milage on every vehicle I've ever owned from my '55 chevy that got 25 mpg, and was a hot rod, to the KIA I have now. My '88 JETTA 4 cyl injected got 38.6 mpg and it didn't matter how fast I drove. My '55 Chevy got great milage whey back when, and if I still had it today, would probably pass smog with out a problem. Why can't auto makers put it together? My 2007 KIA started getting 31 to 34 mpg at around 35K. My 2008 KIA, same model stick shift version 4 cyl, hasn't stepped up to the plate yet, but I'm still at 19K on that one. So some of the claims are right, the 2007 advertised 31 to 34 highway, the 2008 advertised the same. Dealership manager said have patients, some where around 15K you should see it get better. It took 35K for the 2007, so I'll give this one a chance.

9/18/2009 7:03:11 PM

I have a 1999 VW Jetta 2.0 liter. I check the mileage every tank of gs. It's also a great way to keep an eye on the engines health. I get an average of 32 mpg, with that going to about 34 when I take trips. I live in a rural area, and have a 12 mile commute. But I'm very happy with my mileage, and wouldn't trade my VW for anything. My last Jetta got nearly the same mileage, as well.

9/18/2009 2:40:43 PM

I have a 2000 Toyota Tunda 4.7L V8, EPA estimate 14/16 city/highway. I get about 10-11 around town, which is more of the stop and less of the go. I also do a lot of short, 2-3 mile trips where the engine never really gets a chance to warm up. Since I started school, I've been doing mostly highway miles. This tank looks like it's gonna be 12-14 mpg which is all right, but I think an oil change will help. I am also running aggressive all terrain tires, so that probably makes up the other 2 mpgs.

9/18/2009 1:16:09 PM

My 2009 Honda came with a MPG meter built into the dashboard. Keeping a casual eye on it has allowed me to adjust my fuel consumption by adjusting my driving. The bar on the meter reflects consumption from 0 to 60 MPG as you accurate, brake, coast, etc. No more speedy takeoffs or hard braking at stop lights for me!

john harris_6
9/18/2009 12:21:11 PM

I am driving a 2000 Chevy Impala LS with slightly over 200,000 miles. It's 3.8 liter V6 gets better than the EPA estimated fuel economy. I bought that particular model because of the trip computer that came as standard equipment. I leave it set for average MPG. Since I sorted out the problems with its fuel injectors, I have been getting between 30.5 & 31.5 mpg. I drive the car according to the average MPG display. I accelerate gently, coast for most situations of deceleration and brake only when I have to. I bought that kinetic energy. I don't want to waste it by braking.

9/18/2009 10:38:33 AM

Speaking of Ethanol... I have to this date a 1989 Audi 80 that has a damaged fuel injection system due to ethanol, the factory states quite boldly this vehicle must not use alcohol or fuels blended with it. Now that it is out of the test range for emissions, I am going to retrofit it with a carburetor and continue to drive it. I have not been able to drive it since 2001 due to the failure of NoX per mile.(it was off by .02% It passed all the other tests. Don't you just love it? My 2 cents Ethanol is a scam and as mandated, it is not currently sustainable.

9/18/2009 10:26:58 AM

I've always checked millage at fill ups, then average them out once a month or so. I use the trip Odo thing, auto fill on slow tile it clicks off. The usual math thing. I drive a 2008 Honda Fit, 5 speed and I routinely get 37 MPG, this is for combined city and highway. It does top 40 in the summer unless I run the air conditioning, then it falls off to around 35MPG The first fill up I did was in February of 08, snowing and cold. 37 MPG I love this car

topeka ev driver
9/18/2009 10:10:21 AM

I've recorded every tank since the mid 50's in a log book in each glove compartment. Presently averaging 36 mpg on a 12 year old Mercury Tracer station wagon. That's mostly highway miles as we drive our EV's in town. It is sad to look back at log books from cars I drove 40 years ago that got better mileage then most vehicles available today. If your vehicle is 1996 or later you can easily add a ScanGauge II that plugs into the computer port under the dash. It will display your mpg and virtually everything else your vehicle computer knows including trouble codes. You can choose what you like it to display. They have been great learning tools for teenagers learning good driving habits.

keith rosenberg
9/18/2009 9:34:23 AM

I use a spreadsheet and track the mileage I get every fillup. That is one of the many useful things computers can be used for at home.

9/18/2009 9:22:16 AM

My 2009 Honda came with a MPG meter built into the dashboard. Keeping a casual eye on it has allowed me to adjust my fuel consumption by adjusting my driving. The bar on the meter reflects consumption from 0 to 60 MPG as you accurate, brake, coast, etc. No more speedy takeoffs or hard braking at stop lights for me!

9/18/2009 8:10:26 AM

I check my gas mileage every single tank. What amazes me is that some gas stations give better gas mileage than others even when they are in the same family from Shell to Shell or Pilot to Pilot etc.

pat miketinac
9/15/2009 4:00:00 PM

I have checked my mileage for over 40 years for the reasons mentioned. Also, since the 10% ethanol gas came out , I noticed a drop of up to 8% in mileage, some brands better than others, Wal-Mart stations worst at all stations sampled. I guess that is why the sticker says "up to" 10%. There is still one station in my area that has ethanol-free, and that is all I use in my small engines because the ethanol softens rubber parts not designed for it and can loosen gunk in older fuel systems, gumming up carburetors. I had to clean out my mower tank and replace all rubber parts and clean the carb. out. I am concerned that some politicians want to increase the ethanol content above 10%. None of the vehicles that I have checked are approved for more than 10%.

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