3Driving Style

Sitting Still and Idling

Sitting Still and Idling

Did you know that 5-8% of the gas consumed by personal passenger vehicles is consumed while idling?

Avoiding prolonged idling is a good way to improve your fuel economy. All cars get zero miles per gallon when they are sitting still and idling!

Don’t sit in the driveway to “warm up the car.” Modern cars don’t need it. Just drive gently, especially avoiding hard acceleration while the engine is cold. This is the quickest way to warm the engine. When the engine first starts, lubricants haven’t fully circulated; in addition, your oil can be thicker and less effective—especially if it’s also cold outside. This is the time when your engine sustains the most wear, so you don’t want to compound the problem with hard acceleration.

Resist the temptation to de-ice your windows in the winter by running the car for a long time with the defroster blasting. Buy a good ice scraper and allow yourself a little extra time to use it. There may be times when you have to run the car and defroster briefly to keep all your diligent scraping from refreezing, but try not to overdo it. Please don’t drive an ice-covered car using a small peephole for visibility, thinking you’re being “green.” Windows and mirrors are there to give you a 360-degree view, and crashes are very bad for the environment.

Take Action!

  • If you’ll be idling for more than 30 seconds, it's easier on the car and the environment to turn off the engine
  • If you have pulled into a safe location, like a parking lot to make a phone call, turn off the car
  • If there’s any sort of line at all, skip the drive-thru
  • When possible, scrape ice and snow with the car turned off


  • Please do not run red lights to avoid idling
  • Do not do unsafe rolling stops at stop signs
  • Do not ignore railroad crossing signals to avoid waiting
  • It may be unsafe to turn your car off at traffic lights 

Driving Around Town

Driving Around Town

Everyone gets lower fuel mileage around town, and there’s a reason: this is stop-and-go driving. You get the car moving from a dead stop, only to stop it again. It takes energy to get this big mass moving, and then to stop it. You can save fuel and decrease emissions by doing this more gently—by accelerating and braking smoothly with a "feather foot" instead of a "lead foot." In some situations, if you’re traveling the speed limit the lights may be timed to help you.

It is not all about you. You aren’t the only driver on the road. It is not eco-friendly to drive ultra-slowly so that YOU can roll through the next traffic light, if you cause other drivers to brake suddenly or zip around you. Their cars count too. For the other drivers, you need to be predictable. We all expect that those around us will “go with the flow,” driving near the speed limit in good weather, slowing down and allowing more space in the rain, and so on. Be predictable—don’t do strange things that inconvenience or endanger everyone else so you can be green.

Crashes can be tragic for people and the environment, as you will see in the last eco-driving module. A disproportionate number of crashes occur in cities and towns, for many reasons: there’s a lot going on, there’s a lot to pay attention to, and many vehicles and people are concentrated closely together. Interestingly, some of the things you can do to avoid crashes in town can also help you avoid hard braking—paying attention, avoiding distractions, anticipating, and improving your line of sight by allowing enough space between yourself and the car ahead.

Windows versus Air Conditioning
Most people know that using air conditioning requires fuel and thus reduces MPG, but did you know that at higher speeds, it is less fuel efficient to drive with your windows open than with your air conditioning turned on? Experts are not in full agreement, perhaps because the type of vehicle makes a difference, but the consensus seems to be that you’re better off using air conditioning if you’re going over 40 or 45 MPH.

Use your judgment as it may be better to have your window open a crack than to have the air conditioning on even when traveling 45 to 55 MPH. You can be sure that having the air conditioning on the lower settings is better than higher settings and having windows partially open is better than all the way open. Best of all, if it’s not too hot keep your windows closed and vents open.

As a rule, it’s better to have a window open when driving around town than to have the air conditioning on. When you’re on a highway or other high-speed road, using vents is best, and air conditioning is better than rolling down the windows.

Take Action!

  • Imagine that you have a hot cup of coffee between your legs or a gold fish bowl on your dash!
  • Pay attention to the road and other drivers
  • Think about "the other guy"—be considerate
  • Be aware of the air conditioning versus windows tradeoff

Freeway and Interstate Driving

Interstate Driving

Green driving on the highway is a bit of a balancing act between two factors. First, your own car probably gets its absolute best mileage somewhere between 45 and 65, and mileage really drops off above your optimal speed. Second, although you've "seen the light," other drivers may not be eco-driving and may be exceeding speed limits.

So should you routinely drive 48 MPH on the freeway? No! Unless you’re the only one on the road, the smooth flow of many cars is more important to the environment than it is for you to get the highest possible MPG.

If you drive a lot slower than traffic, other drivers may need to jump on their brakes, so be careful about going much below prevailing speeds. Of course, driving the speed limit in the slow lane of a multi-lane highway is perfectly fine. Other drivers may just want to join you. So the green balance is somewhere in the middle—Not so fast as to guzzle gas and not so slow that your behavior is unexpected and disruptive to the traffic flow.

In addition to using fuel efficiently and being predictable, you need to maintain appropriate space around your car. For example, you don’t want to hang out in another driver’s blind spot, or cut in too close when passing a slower vehicle. Be nice and let other cars merge, even those annoying later mergers. This is still eco-driving—it's a community affair. It’s not “all about you” — it’s all about striking a green balance between driving your car efficiently while not hampering other drivers. Being safe trumps everything. 

Cruise Control

Studies indicate that cruise control can increase your MPG substantially when driving on relatively level terrain. However, don't use it on slippery roads. Cruise control is only suitable for low to moderate traffic situations in good weather and on reasonably flat terrain. Even then, it can be detrimental if it leads you to be less attentive, slower to react, or slower to reach the brake pedal in an emergency.

Rural Roads

As a potentially less intense driving situation, this environment may make it easier to slow down a bit and save fuel. On the other hand, windy and hilly rural roads means you will be slowing and then needing to regain speed often. The goal is to do this gently. Anticipation helps. For example, if a car far ahead of you is slowing to turn left, you may be able to ease off the gas early and avoid a full stop.

Help other drivers save gas too. If you’re driving at or near the speed limit, but holding up a long line of impatient drivers eager to pass, consider pulling off the road and letting them go.

Other Eco-driving Modules