Side look of2008 BMW 3-Series 2dr Cpe RWD Blue
Whether or not this feature will come to the U.S. within the same timetable as in the U.K. is unknown. But given the manufacturer's reticence to introduce such gas-saving measures as diesel engines and four cylinders in the U.S. market (conceivably fearing the dilution of its Ultimate Driving Machine image in the power-hungry USA), we'd expect a slower timetable compared to the one in Europe, where the price of gas makes U.S. numbers look like a bargain.
Just like the stop/start systems in hybrids such as Toyota's Prius and GM's Tahoe, the gasoline engine shuts down when the vehicle is stationary. Unlike those vehicles, however, the engine must re-start immediately as it is the only means of propulsion, unlike a gas/electric hybrid. Unknown is whether BMW uses a traditional starter motor in this setup, or an enlarged alternator/starter as in some hybrids.
Predictably, the stop/start feature finds its greatest fuel economy benefit around town, where high cycle stop-and-go driving is common. Presumably, stoplights would offer the greatest fuel savings for the driver of a BMW with this technology.--Colin Mathews