New Fuel-Saving Feature Turns Stop-and-Go Into On-and-Off

(MoneyWatch)  Here's a new definition of stop-and-go traffic: automakers are developing engines that shut off temporarily to save gas while a car stands still, then re-start when the driver steps on the gas.

Drivers with a gasoline-electric hybrid like the Toyota Prius will already be familiar with this feature. The conventional motor turns off as soon as the car stands still for more than a few seconds or even a bit earlier, under hard deceleration at low speeds, such as pulling up to a stop light. Some delivery trucks, including some trucks for the U.S. Postal Service, already do this. Golf carts with an internal-combustion engine work the same way.

Confusingly ?€" by the way, see my earlier entry on Mercedes-Benz's confusing "green" nomenclature, some of which it calls "blue" ?€" parent Daimler AG calls its version of this idea "micro hybrid drive." The thing is, it's not paired with a hybrid gasoline-electric drivetrain. Today, that's what most people associate with the term "hybrid."

The Union of Concerned Scientists has complained that automakers are applying the term "hybrid" to so many different technologies, the term is in danger of becoming meaningless. The group says that using the term to describe this sort of stop-start engine is an example of what they're complaining about.

Anyway, Daimler announced it is adding "micro hybrid drive" to the tiny Smart car, (registration required for full access to Daimler's press site) which runs on an unusual, but conventionally powered, three-cylinder, internal-combustion engine.

In combined city-highway driving, the system gets about 8 percent better mileage, the company said. In heavy, stop-and-go city driving, the stop-start engine saves about 20 percent, according to Daimler.

Initially, the feature is not available in the United States, but a Smart spokesman says they're working on it.