New research from AAA shows that automatic stop-start automotive technology delivers a significant fuel economy benefit. Test results indicated that automatic stop-start systems provide a five to seven percent improvement in fuel economy and reduction in carbon dioxide emissions compared with tests conducted on the same vehicle with the automatic stop-start system disabled.
AAA put three automatic stop-start vehicles through the Environmental Protection Agency’s (EPA) “urban” cycle, which simulates a 11.04 mile commuting trip at an average of 21.2 miles-per-hour. The simulation is mostly urban driving – including frequent stops – and part highway driving. This test was selected to ensure that the stop-start systems worked as they would on a normal commute. A 2013 Ford Fusion, a 2014 Mercedes Benz CLS550 and a 2013 Chevrolet Malibu were tested. The AAA research was conducted with the Automobile Club of Southern California’s Automotive Research Center.
“Up to seven percent improved fuel economy can mean a $215 annual fuel savings* for Southern California consumers,” says Steve Mazor, the chief automotive engineer of the Auto Club’s Automotive Research Center. “It also reduces the main greenhouse gas emitted from cars (CO2) by 5 to 7 percent in city driving,” added Mazor.
Automatic stop-start systems turn off the engine when the vehicle is stopped − such as in traffic or at a stoplight. When the driver releases the brake or the clutch, the engine starts and the car moves forward in drive. While the engine is stopped, systems and gadgets run on power from the vehicle's battery. The feature most often deploys in city driving scenarios – versus highway operation – and may feel slightly different to motorists until they become accustomed to the automatic stop-start sensation. The benefits, however, will not be realized if the feature is turned off.
Automatic stop-start vehicles are still new to North American motorists, and drivers may not be familiar with the features and benefits of this technology. The U.S. EPA and the National Highway Traffic Safety Administration have set standards to increase the Corporate Average Fuel Economy levels to 54.5 (approximately 40 window sticker) miles per gallon by 2025, giving automakers further incentive to escalate fuel-saving technologies. Navigant Research’s 2013 automatic stop-start vehicles assessment projects that only 500,000 of the vehicles sold in the United States in 2013 included an automatic stop-start system, but that number could exceed seven million by 2022.
Additional information regarding AAA’s tests of automatic stop-start vehicles is available on the AAA Newsroom. The study is part of AAA’s Driving Fuel Efficiency series, which also includes the electric vehicle climate study and future fuel-economy studies to help motorists make educated driving decisions.
AAA’s Automotive Engineering team conducts proprietary research to better understand consumer implications of automotive technology, design and functionality.
*Fuel savings are based on driving 15,000 miles a year in a vehicle that averages 20 mpg with fuel prices at $4.09 per gallon. These savings do not include other factors relative to ownership costs of vehicles equipped with automatic stop-start systems, such as potentially higher costs to replace the upgraded battery or starter typically used in these vehicles.