Daimler says that the EPA is underestimating what percentage of time a Mercedes in traffic is in idle mode, when the engine's temporarily turned off. The EPA says that number's about 14 percent, while Mercedes puts it closer to 24 percent. That difference could amount to about 1 mile per gallon worth of rated fuel economy.
Daimler's looking for all of the fuel-economy credits it can get because it can no longer comply with US fuel-economy standards by merely forking over fines. Daimler paid $349 million in fines to the EPA between 1985 and 2011 for missing fuel-economy standards. That was more than 40 percent of the amount paid by the entire auto industry.
As it is, Daimler's fleetwide fuel economy for the 2013 model year is 30.2 mpg, which is up about 10 percent from 2010, but about 10 percent below the feds' 33.1 mpg target, Automotive News says, citing the National Highway Traffic Safety Administration (NHTSA).
As for those glazed windows and their impact on fuel economy? We'll have to get to that another time.