Updated on 12.22.10

Out With The Old, In With The New: Maximize Your Car’s Fuel Efficiency

Trent Hamm

Throughout the month of December, The Simple Dollar is posting a daily series focusing on specific activities you can do right now to set the stage for a great 2011. Out with the old, in with the new.

23. Maximize your car’s fuel efficiency.

Over the last five years, we’ve put an average of 20,000 miles a year (combined) on our vehicles. When you’re driving that many miles, even a little bit of fuel efficiency makes a huge difference.

For example, if we’re getting 15 miles per gallon and I discover a way to get that mileage up to 16 per gallon, suddenly we’re burning through 83 gallons of gas less per year. At $3 a gallon, that’s $250 a year in gasoline savings.

If you can make a bigger jump – from 15 to, say, 20 miles per gallon – you’re saving more than $1,000 per year if you drive as much as we do.

That can be a huge savings, particularly when most of the choices you make don’t really impact your day-to-day life. Here are eight specific steps you can take to improve your fuel efficiency.

Shop for fuel efficiency. When you’re looking for a replacement for your current car, keep a serious eye out for fuel efficiency. Use sites like FuelEconomy.gov to find out the fuel efficiency of the models you’re considering and give an extra look to models with better fuel efficiency. If you can buy a car with 5 miles per gallon more efficiency, you’ll save significant money every year you own it.

Don’t speed. When you’re speeding, your car uses fuel much less efficiently. A car traveling 75 miles per hour is much less fuel efficient than a car traveling 55 miles per hour. Beyond that, you also run the risk of acquiring traffic tickets if you speed, which not only have their own cost but also increase the cost of your insurance.

Maintain even acceleration. You eat gas whenever you press down the gas pedal in your car. The most efficient way to drive is to maintain even acceleration, meaning you don’t push the pedal down and you don’t let it up, either. Cruise control works for this if you’re driving where it’s flat, but if you’re in a hilly area, you’re better off doing it yourself, speeding up on the downhill slope and slowing down when going uphill.

Air up your tires. Fill up your tires to the maximum recommended pressure in the owner’s manual in your automobile, which takes into account the mass of your car. Every pound of pressure that you’re low in any of your tires results in a 1/8% reduction in fuel efficiency – and almost everyone’s tire pressure is at least five pounds low per tire. If that’s true for you, just airing up your tires would result in at least a 2.5% increase in fuel efficiency – it’s like going from a 20 mile per gallon car to a 21 mile per gallon car. I check my pressures every month.

Minimize your car’s weight (unless it’s winter). The more weight your automobile is carrying, the more work the engine has to do and the less fuel efficient your car is. The best solution is to minimize your car’s weight, which is a good idea when the roads aren’t slick.

Use the right kind of motor oil. Read your car’s manual and make sure that whatever service you’re using to get your oil changed is putting the right kind of oil in your car. Using the wrong kind of oil can result in a 2% loss in fuel efficiency for your car (on top of other potential problems).

Turn off the ignition instead of idling. If you’re sitting for more than fifteen seconds, turn off your car’s engine rather than just idling. Idling eats up gas – it’s essentially burning money. I turn off the engine even at some stoplights, but I always turn it off when waiting on trains, in traffic jams, or waiting on accidents.

Use a warehouse club. This is the single best principle I’ve found for saving money directly on the gas you buy. Over the course of a year, we pay for a Sam’s Club membership solely through the gasoline savings. Our local Sam’s Club offers gas at least $0.04 per gallon less expensive than each of their competitors. If we use 1,000 gallons of gas over the course of a year, there’s the $40 for our membership. Any savings we actually get for anything else is subsidized just by the gas.

Saving money on your car’s fuel efficiency is a great way to cut down on your costs in the coming year. Best of all, most of the methods are things you can do just once and reap the rewards from for a long time.

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  1. Kevin says:

    “When you’re speeding, your car uses fuel much less efficiently.”

    I appreciate the point you were trying to make here, but I think it’s a little oversimplified.

    Most cars achieve maximum fuel efficiency at around 50-55 mph. So while you’re correct in pointing out that going 75 mph in a 55 zone is not only dangerous, but also very inefficient, it’s also true that going 55 in a 45 zone is INCREASING your fuel efficiency.

    Think about it. Crawling along at 5 mph in rush-hour traffic is terribly inefficient. Likewise, obeying the speed limit in a 15 mph zone is operating your car at well below maximum fuel efficiency. In this case, speeding (up to a maximum of 55 mph) actually INCREASES fuel efficiency (though clearly is unsafe).

    Ignoring the safety aspect of the argument, it’s inaccurate to make the blanket statement that “When you’re speeding, your car uses fuel much less efficiently.” A more accurate statement would be, “Traveling at any speed other than 55 mph, your car uses fuel less efficiently.”

  2. KC says:

    I’ve bought gas as much as 10 cents less per gallon at Costco – but it is usually around 5 cents less.

    Don’t forget that speeding is simply not safe. My car is as efficient at 55 mph as it is at 80 (I’ve tested it several times – always 32 mpg) But I’m much less safe if I’m going 80 than 55 depending on the traffic situation. Safety will always trump everything else I do in life, but generally I go a few miles above the posted speed limit if conditions and traffic allow on the interstate. I get both maximum mileage and time efficiency that way.

    I’ve also heard others discuss the merits of different grades of gasoline on their mileage. The guy who buy my 1989 Nissan Stanza swore that he got his best mileage out of mid-grade (specific brand) gasoline than he did any other grade or brand (I can’t remember the brand he used). He said it’s car specific and he’d test the Nissan to see what worked best for it. I’m not sure I have the patience to test all those brands, but I have done some grade testing. My car, which advises you use premium fuel, does burn more efficiently by using premium gasoline. I’ve done the math and I am better off paying for premium as my car burns it at a more efficient rate than 87 grade. No more than I drive the savings aren’t that great, but it might be worth it to run some tests of your own if you drive a lot.

  3. Tyler says:

    Read your owner’s manual to determine the speed for peak fuel efficiency. With my 2009 Chevy Malibu, I average 34 MPG when traveling at 70-75 MPH, but have only 29 MPG when traveling at 55 MPH.

  4. Eric says:

    “Turn off the ignition instead of idling. If you’re sitting for more than fifteen seconds, turn off your car’s engine rather than just idling. Idling eats up gas – it’s essentially burning money. I turn off the engine even at some stoplights, but I always turn it off when waiting on trains, in traffic jams, or waiting on accidents.”

    I’m not sure I would agree with this. Turning over the engine to start it back up requires a significant amount of electricity to power the starter motor. Naturally, this energy is pulled from the car’s battery. Even though the alternator is recharging the battery as you drive, this puts extra wear and tear on your battery, and extra wear on your transmission. It might save gas but it could cause you to need additional maintenance more quickly than you would have otherwise.

  5. jim says:

    Drive less.

  6. John says:

    I question turning the engine off. Restarting will add wear to the starter, and thus hasten the day it needs to be replaced. Starters are NOT cheap to replace–easily a few hundred. With long enough waits, I guess one would save more. But shutting off regularly for a 30 second light? I’m not so sure.

    Issue #2 with turning the engine off–what happens if you can’t get it started again? This, alone, is why I never, EVER, turn an engine off in traffic.

    With gas, one concern may be quality of fuel. Some mechanics say that not all gas is the same, and some cheap brands may hasten problems with fuel injection systems. Which could easily negate any savings.

    Finally, the best savings is not driving. Parked, a car uses no fuel. Thus, the less one drives, the better. Plus, this can result in lower insurance rates, and will lower maintenance costs.

  7. Mule Skinner says:

    Re: Turning the engine off while waiting: Isn’t this what the Prius does automatically? Can we therefore conclude that it’s going to wear out starters faster than other cars?

  8. deRuiter says:

    Maximixe the number of things you accomplish per trip. If you need eggs and you’re passing the market on the way to something else, stop and get those eggs. Plan your driving routes to take advantage of shortest, most efficient routes. Combine errands, carpool, even on errands. In warm weather, for close to home stops, take your bike, or walk the dog to the place you need to go.

  9. Jules says:

    “Maintain even acceleration” – should be “maintain even (better word, steady) velocity”. Minor quibble, but strictly speaking acceleration refers to a change in speed so by maintaining an even acceleration that would mean increasing your speed by, say, 5 mph every minute. On a long trip, that could mean approaching the speed of light :-)

  10. SupportingParents says:

    Has anyone tried fuel chips? If so do they work and what brand? They are supposed to increase fuel efficiency and I would love to try one but don’t want to waste money if they don’t actually do anything.

  11. sm4k says:

    The best way to tell if you’re maximizing you’re fuel efficiency is to log it each time you fuel up.

    However, if you’re a bit lazy and you’ve got a car that supports dual trip-odometers, reset one every time you fill up your fuel. You can use this as a easy way to gauge how well you’re doing on the fuel conservation front. I do this and used to always try to beat 400miles per tank. Now I can routinely beat 420 miles a tank, though going much further than that leaves me a bit uncomfortable that I may run out.

    This has the added benefit of giving you a heads up when something may be wrong with your car, since a lot of times a loss in MPG is the first indicator that there is a problem. If I was to get 350 miles per tank one week, I’d be suspicious. Two weeks in a row, and I’d have a mechanic look at it.

  12. David says:

    Accelerating at 5 miles per hour per minute, you would have to make quite a long trip to reach the speed of light – just over eleven million miles, or about 235 times the total length of the highways in the United States. At 400 miles per tank, you’d need to refuel about 28,000 times.

    One good thing: as you approach the speed of light your vehicle will contract in the direction of motion, making it more difficult for speed cameras to detect (and, of course, for police cars to catch). Unfortunately your mass will also approach infinity, which will be counter-productive in terms of your weight-loss program.

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