How to improve gas mileage
Aug 08 '00 (Updated Dec 31 '03)
The Bottom Line Taking small maintenance steps and changing driving habits can have a big impact on fuel economy.
With the coming of summer, the price of gasoline takes it's yearly climb. While prices aren't predicted to be as high as they have been in the past, you can still save money and do your part to help the environment by improving your car's fuel economy. Not everyone realizes that it's easy to improve your gas mileage, without resorting to chemical additives or other tricks and gimmicks.
The first thing to cover is how to measure gas mileage in your car. Many modern cars are equipped with in-dash computers that can tell you on the fly, which are excellent for determining exactly how your driving habits impact fuel consumption. However, without this amenity, you'll need to do some math. First, fill your tank up with the grade of gas you regularly use. Do Not 'top off' your tank, stop filling when the pump automatically turns off. Before starting your car, reset your trip odometer to 0, or if you don't have one, mark down the mileage on your odometer. Drive as you normally would, and next time you pull in for gas, make a note of how many miles you've traveled. Fill up your tank again, without topping it off, and look at the pump to see how many gallons you added. This is how many gallons you've used over the mileage you've driven. Now, simply divide the number of miles traveled by the number of gallons of fuel, and you have your fuel economy. Doing this every time you fuel up can give you a starting point for making driving decisions that improve your fuel economy. Here are some important ways to begin:
Go on a Diet: Not you, the car! Basic laws of physics tell us that it takes more energy to move a greater mass. This means that your vehicle requires more fuel to move a heavier load. If you constantly carry lots of junk around in the backseat or trunk, removing it can have a great impact on how much fuel your vehicle uses. Try to carry only necessary items, such as an emergency kit, blanket, and other necessities. Try measuring your fuel economy before and after reducing the load, and see what a difference it makes. This is especially important in smaller, lighter economy vehicles - removing 50 pounds of stuff from a 3500 pound vehicle is a much smaller difference than removing the same amount from a 2400 pound car with a teeny tiny engine.
Check your Tires: Under inflated tires can not only harm your gas mileage, but can also put you at greater risk of a blowout while you're driving, and lead to premature wear (that means money!). Check your tire pressures at least once a month, and make sure they are at the manufacturer's recommended levels. Don't make the mistake of over inflating your tires in an attempt to pinch pennies; it's also an unsafe practice. During periods of high temperature changes, such as spring and fall, it is very important to check tire pressure often. A difference in the air temperature inside and outside the tire can affect the pressure without any air moving in or out of the tire.
Perform regular maintenance: There's a reason your owner's manual tells you to change the oil, spark plugs, air filter, and other components regularly (you have read the owner's manual, right?). Proper maintenance not only can help save fuel, but can even save your wallet in costly repairs down the road. Check your manual for the proper intervals for this maintenance, but motor oil, spark plugs, and the air filter are the three key elements here.
Dirty motor oil not only reduces engine life but creates friction within the cylinder and other engine parts. Increased friction means more energy is required to operate the engine, and where does this energy come from? That's right, your fuel.
Spark plugs can get dirty or worn, and should be checked for this often. Not only can a dirty plug signal other impending engine problems (which you can then fix before they cause worse damage), but they reduce the efficiency of the combustion process within the cylinder. This means that you aren't getting the maximum energy out of your fuel, and to make up for it you need to burn more of it.
The air filter removes large particles from the air that is drawn into the engine and mixed with the fuel before combustion. This prevents those particles from harming the moving parts. As the air filter removes these particles, it becomes more and more clogged, and the air that is taken in is more and more restricted. Keeping proper airflow helps to maximize the combustion process, helping you get the most possible energy from the fuel.
The following suggestions are based on the fact that a lower engine speed (RPM, Revolutions Per Minute) means less fuel is being used by your vehicle. Smooth driving will keep your engine at lower speeds more regularly, and can end up saving you in the end.
Avoid jack-rabbit starts: Some people floor the accelerator whenever they go from a stop. Sure, they might get to test the 0-60 time of their car from every light, but they're really wasting a lot of gas. If you ease on the gas and start more slowly, you won't bring your engine into higher RPM ranges, and you won't use as much fuel.
Upshift as soon as possible: In a vehicle with a manual transmission, experiment to find out how low you can shift without lugging the engine. The lower you shift, the lower speeds your engine will maintain, and the less fuel it will use. In addition, by putting the transmission into top gear as soon as possible, you are using the mechanical advantage of gear ratios to do the work, rather than making the engine burn extra fuel. Shifting too soon (at too low RPMs) can harm your engine, especially under a heavy load, so experiment to see what is best for your vehicle. Some cars even have shift lights for this purpose, to tell you when is a good time to shift for maximum economy.
In an automatic, it's somewhat different, but this technique is still applicable. Most automatic transmissions have a specific RPM point below which they will not upshift. Once you find this point, you can 'force' the car to upshift as early as possible simply by being easy on the gas. Letting off the gas a bit will signal the transmission to upshift, at which point you can ease on the gas again. Avoid stomping on the accelerator in an automatic, as this will signal to your transmission to downshift, putting your engine into a higher RPM range. Increasing speed smoothly and slowly will get you to your destination without taxing your engine or wasting fuel.
Avoid Idling: When you idle you car, you're getting zero MPG. At some points, such as long lights and slow traffic, it's impossible to avoid idling (Do not turn your car off in situations like these. Regardless of whether or not it saves fuel, it can be dangerous for you and other drivers). However, when starting your car, you don't need to idle it to warm it up; most cars built within the last 15 years or so are ready to drive as soon as they are started. Also, when making 'quick stops' at convenience stores, etc, shut your car off instead of leaving it idling.
In addition, try to avoid making stops whenever possible. If you have a choice between two routes, one which has 5 stop signs, and one which is slightly longer but has no stop signs, the second route will save fuel. Starting from a complete stop uses 50% more fuel than starting from only 10mph. This does not mean you should coast through stop signs, but you should plan your route intelligently to avoid things which may hurt your fuel economy.
Consider a standard: If you're in the market for a new car and want better gas mileage, you might want to check out a stick-shift over an automatic. On the whole, they get better gas mileage, and if you ask me are more fun to drive. Not only do you have more control over when and how your transmission shifts, but a manual generally has one or more additional gears than an automatic (five or six versus four or five) for the same model vehicle. These additional gears give you better choices for a wider range of situations, and often the top gear is 'taller', which will provide a lower RPM for the same highway speed as compared to an automatic. For more info on this, see my other article, 'manual vs. automatic'.
As you've probably picked up by now, the simplest way to improve gas mileage is to change your habits. Using the advice above, you should see an improvement of at least 3-5 mpg, and in some cases you can even save 10 mpg or more! Not only will this save you some money, but it will lessen the impact of your vehicle on the environment, and most of these tips can help lengthen your car's life. Good luck and happy driving!
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