Though idle-stop technology has been available on European cars for years and is projected by the EPA and NHTSA to be included on a whopping 42 percent of vehicles by 2016, there are currently only three non-hybrids offering the feature in the United States: the BMW M3, and the Porsche Cayenne and Panamera models. Unfortunately, these 2011 models using idle-stop get absolutely no boost in MPG on window stickers, or for CAFE standards, compared to 2010 models without idle-stop. This is despite the technology’s great promise to improve efficiency at a modest cost.
Idle-stop, or stop-start as it’s often called, shuts down a car’s engine completely when it isn’t needed. The engine restarts when the driver accelerates. The feature can provide fuel savings of 5-10 percent at an added cost of as little as $300.
With gas prices threatening to surpass record highs this summer, mainstream American consumers who could take advantage of the system’s cheap mileage boost are out of luck. The only vehicles offering stop-start are hybrids and luxury models priced beyond the range of the people hardest hit by rising fuel costs.
The lack of incentives for automakers to add idle-stop technology here will keep sales in North America well below Europe and Asia, according to John Gartner, a senior analyst at Pike Research. “With nearly 50 models to chose from, European customers are expected to buy nearly 3 million idle-stop vehicles in 2011,” Gartner said. “American consumers would also embrace vehicles that don’t burn fuel when stopped if they had similar options.”
So why is one of the most inexpensive yet powerful fuel-saving technologies in existence not available on mainstream vehicles? Partly because the EPA and the National Highway Traffic Safety Administration don’t count it towards the official fuel economy rating of a vehicle—meaning that carmakers get no credit for the boost in their CAFE ratings or on EPA window stickers. In other words, automakers have no incentive to add idle-stop.
BMW first offered stop-start on its M3 this year, but neither its city nor highway rating improved a single MPG over the 2010 model. The Porsche Panamera and Cayenne’s fuel-economy ratings did improve, but as a result of a new engine, better aerodynamics, and standard low rolling resistance tires—not the idle-stop systems.
Blame the Test Cycle
During the EPA’s test cycle, a vehicle
comes to a complete stop only once, leading to just a 0.1 to 0.2 mpg improvement in fuel economy. (Update: On the CAFE urban test cycle, the car is idle has about 19 percent of the time, or 10 percent for combined highway/city. The European test cycle has approximately twice the idle time, and those EU idles are much longer in duration, which increases the benefit. Overall, the benefit of idle-stop on the EU cycle might be about three times that on the US cycles.)
So it’s not that there is no benefit US test cycle, just not huge, and much lower than Europe. Depending on how it was implemented, the BMW and Porsche models could have receive only a 1-2 percent improvement, which may not have been enough to cause a 1 mpg change on the label. Nonetheless, the cars could have received some benefit for CAFE.
European tests include more stops—explaining why the technology is on the verge of being widespread in the EU—and the EPA has promised for several years to refine the its test procedures, but so far no announcement has been made.
The good news is that things could soon change—at least if Ford and GM’s production schedules are any indication. G.M.’s new eAssist mild hybrid powertrains and Ford’s appropriately named Auto Start-Stop system feature idle-stop technology, and both will debut by the end of next year.
Still, the failure of American regulators and carmakers to incentivize such a simple and inexpensive fuel-saving solution in time for $4 gas is a shame. Consumers are flocking to small, inexpensive vehicles like the Chevy Cruze and Ford Fiesta, which tend to get outstanding fuel-economy on the highway but are not impressive in the city—where stop-start is most useful. For the time being though, consumers looking for substantial gas savings at an affordable price may be best suited to look for a used hybrid.