Obviously, economy modes are intended to save gas. But how do they do it? We break it down.
Eco, Econ, or economy modes have become common in modern vehicles. These driving modes are intended to save you fuel, but how do they actually work, and how much can they save you? The first question is one we can answer, but the second, how much you’ll save, is a bit trickier.
Enable the economy mode in your vehicle and the first thing you will notice is that the power pedal changes. We’d call that the “gas pedal”, or “throttle” but electric cars have economy modes too, use no gas, and have no throttle. The pedal can change in its feel, or how it makes the vehicle respond. You may notice that the pedal feels harder, or that when you press down, you get less punch for a given amount of travel. The power pedal on a modern car is just sending a signal to the car’s computer, not mechanically adjusting anything under the hood. The most significant effect that economy mode has is to mute your request for acceleration. Not only does the power pedal change, the car adjusts how and when the transmission shifts up and down (if it has one).
“Econ Mode helps you to drive more gently,” says Chris Naughton, Northeast Regional Public Relations Manager of American Honda Motor Co. Slower acceleration and less power input mean less energy is expended. Whether your vehicle is gasoline or electric powered, this is the primary key to improving your fuel economy. Mr. Naughton explained to us in detail how Honda’s newest green vehicle, the Honda Clarity Plug-in Hybrid, manages power using the various modes, saying,”In Econ mode, changes made to the map governing system output promote full-electric driving. Once battery energy is depleted, changes made to the throttle map encourage drivers to use less of the available performance, thereby potentially extending the practical driving range compared to Normal mode.”
That’s a lot to digest. In essence, the Econ Mode takes a very active role in what happens when you push down on the power pedal to ensure the best use of the car’s elaborate drive system. But how much more fuel or electricity is saved by using these modes? Honda won’t say, nor will other automakers because it can vary based on how you operate the vehicle while in Econ Mode. For example, we all know that an engine made “slower” by a hard power pedal may be unsafe in some situations where going faster may be the best way to avoid trouble. Automakers thought of that. “Full vehicle power is always available with a full press of the pedal,” notes Mr. Naughton. So, if you floor it, the car will still instantly ignore all of its best instincts and give you all the power the drivetrain can produce. It also negates any gains you may have been getting by driving around in Econ Mode.
One clue to just how much savings might be there is provides by FuelEconomy.gov, the U.S. DOE and EPA’s website for all things fuel economy related. In its section titled “Driving More Efficiently,” the site says that aggressive driving can consume 10% to 40% more fuel than sedate driving.
HVAC Control Changes
The second most important way that economy modes alter your vehicle’s settings to save energy is by taking control of your heat and air conditioning. Running an AC compressor and the fans in your car consumes a lot of energy. Economy modes do a variety of things to cut back on that consumption, while still keeping the driver comfortable. You noticed we said “driver’ and not “occupants” plural. That’s because one easy way to reduce the power needed by your HVAC system is to direct all of its effects on just the driver. Toyota’s Prius has Smart-Flow climate control technology that automatically senses where occupants are located in the car and cuts the HVAC to those areas that are not occupied. In economy mode the HVAC system may also allow for a greater fluctuation of temperatures. For example, if you have the system set to 70F, in economy mode it may range from 70 to 74F in cooling modes. Most modern cars also recirculate cooled air automatically, rather than only when a driver requests it. This reduces the amount of air the car needs to cool.
Cruise Control Changes
Modern cruise control systems do much more than just try to keep a car on or above a certain set speed. They can follow a car in front of you and speed up and slow down and they can also slow your car when you are on a steep decline. When you select economy mode, the car’s computer will allow for a greater variation in your speed. Although you have the system set for 65 MPH, you may notice that in economy mode it will sometimes drop to 63 or 62 MPH heading up a hill. Similarly, when a slowpoke ahead of you exits and your lane becomes clear, the car will return to its set speed more gradually than if you were in normal mode. These actions save you energy.
In some vehicles, using the economy mode will change the dash display. A new look will appear that shows colors or graphics indicating how efficiently the driver is operating the vehicle. FuelEconomy.gov says that, “A recent study suggests that they can help the average driver improve fuel economy by about 3% and that those using them to save fuel can improve gas mileage by about 10%.”