Mercedes-Benz will get extra credit on U.S. fuel economy standards for putting start-stop systems in its luxury cars -- but not as much as the automaker had hoped.
In a ruling released in September, the EPA signaled that it remains uncertain about the benefits of start-stop systems, which usually turn off the engine when a vehicle comes to a stop and restarts it when the driver lifts his or her foot from the brake.
But the ruling suggests the EPA is willing to reward car companies in the form of credits -- good toward compliance with the agency’s standards -- if they can prove that their customers’ start-stop systems are indeed cutting pollution.
“Retroactive credits may be granted,” the EPA says in its ruling, “if supported by actual real-world customer vehicle data.”
Start-stop systems, sold by Tier One suppliers such as Bosch, Continental, Delphi, Denso and Valeo, are a key part of auto companies’ strategy for meeting strict new emissions regulations around the world. That includes the latest U.S. standards, which require an automakers' new cars and trucks achieve an average of 54.5 mpg by the 2025 model year.
Getting credit for the use of start-stop systems is especially important to Mercedes-Benz, which relies on selling luxury cars with powerful gasoline engines.
The company paid $349 million in fines for falling short of U.S. fuel economy requirements from the 1985-2011 model years. But under new fuel economy rules, paying fines is no longer an option.
To help its case, Mercedes-Benz submitted a petition last September seeking “off cycle” credits, which reward automakers that improve efficiency through technology that does not show up on the standard city-and-highway test cycle.
In last month’s ruling, the EPA gave Mercedes-Benz most of the extra credits that it requested -- for use of high-efficiency lighting, ventilated seats and infrared glazing on windows -- but drastically scaled back its request for start-stop credits.
Without submitting an application, car companies can receive credits worth 2.5 grams per mile for cars and 4.4 grams per mile for trucks.
Mercedes had asked for 9.1 to 19 grams per mile, citing data showing that vehicles spend more time idling than the EPA originally thought.
“There is a real savings here, and we have been able to definitively prove it,” William Craven, the general manager of regulatory affairs at Mercedes-Benz parent company Daimler AG, said last year in an interview with Automotive News.
Regulators largely agreed with that, but fretted about something else: how often the start-stop system actually turns off the engine. When the climate control system needs power, for instance, the engine may not idle.
As a result, the EPA awarded Mercedes-Benz credits equal to just 3.6 to 4.3 grams per mile -- only a little more than what the company could have received without submitting a petition.
In its ruling, the agency said that it used a “conservative” estimate of the system’s effectiveness at turning off the engine. It asked Mercedes-Benz to come back with more specific data, suggesting that Mercedes-Benz may well prevail because the agency is “very likely underestimating the overall system effectiveness.”