How much do you know about saving gas? Test yourself (and your coworkers) with these true-or-false statements.
- The shape of your tires influences gas mileage.
- You can save gas by filling your tires with nitrogen.
- Carrying more passengers burns more gas.
- Use a premium gasoline to improve your mileage.
- To improve your gas mileage, let your engine warm up before driving.
- You'll use less gas if you keep the engine running for 1 minute than if you stopped and restarted the engine.
- Use overdrive gears to improve mileage.
- Cruise control saves gas.
- You can save gas with fuel additives or devices.
- The last time you had a checkup can affect your mileage.
- Running your air-conditioner can help your gas mileage.
- Driving with your pick-up truck tailgate down saves gas.
Okay, now scroll down to check your answers:
1. The shape of your tires influences gas mileage.
TRUE. Keeping your car's tires properly inflated AND aligned can improve mileage 3 percent. The EPA estimates a car tire that's 2 PSI under-inflated burns 1 percent more gas. Check your owner's manual for the correct PSI for your tire; what's imprinted on the tire may not be right for your vehicle. (You can also help by reducing the load on those tires. Every 100 pounds of extra weight in your vehicle can reduce gas mileage by 2 percent. Smaller vehicles will benefit more from reducing the load than larger vehicles.)
2. You can save gas by filling your tires with nitrogen.
TRUE -- but only because they keep your tires properly inflated longer. Nitrogen leaks from tires slower than compressed air, keeping your tires at the proper shape, and it also reduces the aging of rubber tires. Whether using nitrogen instead of compressed air improves gas mileage under normal driving conditions was studied by the U.S. National Highway Transportation and Safety Administration and Canada's transportation department; both studies were expected to be completed in early 2007 but as of June the results of those tests aren't available.
3. Carrying more passengers burns more gas.
TRUE. Any additional weight in your car reduces your mileage. But this shouldn't be used as an argument against car pooling. The fewer cars on the road, the less gas you're using and the less pollution you're creating. It's cheaper for four people to share the cost of one car burning gas than to pay for four cars burning gas. For the environment's sake, it's better to find other ways to reduce your car's weight, such as cleaning trash from the back seat, taking off the ski rack or bicycle rack when not in use, and removing anything that isn't essential from the trunk.
4. Use a premium gasoline to improve your mileage.
FALSE. Unless your engine is knocking, save your money with the less expensive, lower octane gas. Higher-octane, premium fuels help prevent the damaging "knocks and pings" in your engine, but most modern engines are designed to do that themselves with electronic fuel injection and monitoring your engine's combustion. You should only use premium gas if your car's owner manual specifically requires it. If the manufacturer "recommends" premium, your car might be fine with regular; check with your dealer.
5. To improve gas mileage, let your engine warm up before driving.
FALSE. You can pull out of the driveway as soon as you start your car. The engine warms up faster when it's moving, not idling. Since warmer engines are more efficient and put less wear on your engine, it's another good reason for combining as many errands as you can into one trip.
6. You'll use less gas if you keep the engine running for 1 minute than if you stopped and restarted the engine.
FALSE. Idling for 30 seconds uses more gas than starting the engine. So if you're running in for a quick errand, or stopped at a drive-up ATM, you'll save gas by shutting off the engine.
7. Use overdrive gears to improve mileage.
TRUE. Overdrive uses less fuel by forcing your engine speed down. It not only saves gas but reduces wear on your engine.
8. Cruise control saves gas.
TRUE. You can improve mileage by driving at a constant speed, which cruise control can do better than many drivers. Other good driving habits will save mileage, too, like gradual acceleration and braking instead of "jack rabbit" starts and hard braking. Speeding and other aggressive driving on the highway can use 33% more gas.
9. You can save gas with fuel additives or devices.
FALSE. The Environmental Protection Agency has tested dozens of these for the past 30 years and found no proof that most of them work; even those that did work showed only marginal improvement. Consumer Reports tested Fuel Genie, Tornado, and the Platinum Gas Saver, and didn't see any improvement in gas mileage. These devices can cost $100, and even if they did work, they would need to offer more dramatic improvements for you to quickly recoup your savings. You're better off using the money to fill your tank.
10. The last time you had a checkup can affect your mileage.
TRUE. The gas mileage on the sticker when you bought your car was based on a well-tuned, properly maintained car. A tune-up today can improve your gas mileage 4 percent -- and up to 20 percent if your car has been poorly-maintained. A clean air filter can improve your mileage 10 percent over a clogged filter. Using the manufacturer's recommended grade of motor oil also improves mileage -- and look for "Energy Saving" on the performance symbol; these oils contain friction-reducing additives that further improve mileage. And of course with a checkup, they'll check the tires.
11. Running your air-conditioner can help your gas mileage.
TRUE and FALSE. Sorry for the trick answer, but the jury is out on this one. Originally, we cited a Consumer Reports article which said yes it does at highway speeds because it reduces drag. That article has been removed and a more recent Consumer Reports article found the drag on gas mileage when the windows were rolled down "made no significant difference." An article from the respected Edmunds.com also recommends using A/C at highway speeds but in a more recent article editors put this to the test and found no measurable difference in gas mileage whether they used the air-conditioner or rolled down the windows as long as the sunroof remained closed.
A search of the Web will find professional automotive organizations such as the National Institute for Automotive Service Excellence supporting using the air-conditioner at highway speeds, and personal experiences both supporting and refuting it.
In 2008, the EPA's vehicle mileage tests will add more real-world conditions, including driving a vehicle with the air-conditioning on.
12. Driving with your pick-up truck tailgate down saves gas.
TRUE. Driving with the tailgate down improves the truck's aerodynamics. By some estimates it will improve your gas mileage up to three percent -- but only if the truck bed is empty.
Sources:
FuelEconomy.gov
http://www.fueleconomy.gov
Federal Trade Commission: "How to be Penny Wise not Pump Fuelish"
http://www.ftc.gov/bcp/conline/pubs/alerts/fuelalrt.pdf
EPA: Gas Saving and Emission Reduction Devices Evaluation
http://www.epa.gov/otaq/consumer/reports.htm
Consumer Reports magazine fuel economy guide
http://www.consumerreports.org/cro/cars/ratings/a-guide-to-stretching-your-fuel-dollars/index.htm
U.S. General Accounting Office
http://www.gao.gov/new.items/d07246r.pdf
