When BMW switched from an inline six-cylinder engine to a turbocharged four-cylinder for the 2012 BMW 328i sedan, there seemed to be a positive tradeoff in that the new, smaller engine would be able to deliver just as much power as the outgoing model, yet offer an astounding 36 mpg highway. Indeed, when we tested it, we thought that was highly possible, as we weren’t being gentle with it, and we still were averaging around 30 mpg in higher-speed driving.
The Environmental Protection Agency shared neither BMWs nor our enthusiasm for the engine’s fuel sipping capabilities, reducing that number this week to 33 mpg for the 2012 BMW 328i sedan with its new eight-speed automatic transmission. The agency also took city fuel economy down by one from 24 mpg to 23. It should be noted, however, that numbers have not been adjusted on the EPA’s fueleconomy.gov website as of the time of this writing.
“We really don’t know what went wrong,” says BMW spokesperson Tom Plucinsky, noting that the car BMW delivered to the EPA was the same one it had used in its certification testing.
Plucinsky said every year, automakers supply a handful of cars for verification to the EPA. BMW does most of its fuel economy testing in-house, but gave its new 328i over for testing among a small sample of other vehicles to the EPA in Ann Arbor, Mich. In years past, BMW has seen numbers go up or down “mostly from rounding errors.” But it’s never seen anything along the lines of a 3 mpg reduction.
“It’s odd because we’ve seen in real-world testing it can deliver those kinds of (36 mpg) numbers,” Plucinsky said.
He added that BMW would not be able to contest the EPA’s findings in the middle of a model year or have the car retested until next model year. He said that no other vehicle with the new twin-turbocharged 2.0-liter four-cylinder engine will have its numbers readjusted—not even the six-speed manual version of the 2012 BMW 328i sedan, which will retain its 23 mpg city/34 mpg highway rating. It should be noted that in addition to the manual 328i, none of the other four-cylinder models, which include the BMW Z4 sDrive28i, 528i, and X3 xDrive28i, were independently tested.
Despite the fact that even with a reduced rating, the BMW 328i is still the most fuel-efficient entry in the compact luxury class, BMW isn’t planning to stand still, as the reduction will likely also lower its corporate average fuel economy (CAFE) numbers, too.
“We don’t have any answers yet, but we’re taking a serious look at it,” Plucinsky said.