A BMW spokesperson has confirmed to us that the manufacturer will have to lower its fuel-economy estimates for the 2012 328i automatic. The numbers drop from 24 mpg in the city and 36 on the highway to 23/33. Why the new figures all of a sudden? It has to do with the EPA’s fuel-economy validation process.To get a car rated, Automakers run it through the EPA’s testing procedures and then submit their own fuel-economy numbers to the government agency. (For a full explanation of the EPA’s testing procedures—and how complicated they are—read our story, The Truth About EPA City/Highway MPG Estimates.) In most cases, the EPA takes those numbers from the manufacturer and declares them official; sometimes, however, the agency will test a car itself. Ultimately, only about 15 percent of all cars sold in the U.S. are actually tested by the EPA, and the new 2012 328i with the automatic transmission is one of those cars.
A BMW representative told us the EPA tested the exact car the automaker used in its tests in Munich: a U.S.-spec 2012 328i with the eight-speed automatic. As prescribed by the EPA, fuel-economy testing takes place indoors in a controlled environment. The car is strapped to a dyno, and specific EPA-approved fuel is used during the five test cycles: city, highway, aggressive highway, hot city, and cold city. As to the sizable discrepancy in this case, there’s really no way to explain the differences in the ratings without BMW or the EPA opening up, and we don’t expect that to happen any time soon. According to BMW, the 2012 328i auto can’t be re-tested until the 2013 model year per EPA regulations. Until then, BMW will advertise the EPA’s lower 23/33 mpg estimates for the automatic-equipped 328i.
As for the six-speed manual 328i, it keeps its 23/34 mpg figures. We see this as another opportunity to make a case for the stick, our 3-series transmission of choice.