BMW unveiled a 7 Series hybrid concept car and while it's a concept car that's due to be announced in a week at the Paris Auto Show, it's really a thinly disguised (with lots of decals) mild hybrid version of what will be available late in 2009 as a production vehicle. The best news: In city driving, you might see 30 mpg. That wouldn't excite a Toyota Prius owner, but then the Prius doesn't have a 407-hp twin-turbo V8 engine, either. The hybrid concept is based on the next generation, 2009 BMW 7 Series that is the world's best high-end sports sedan. Here's what you'll likely get with the 7 Series hybrid:

-- The main engine is BMW's 4.4-liter V8 with twin turbochargers, producing 407 hp and 442 pound-feet of torque. BMW says this engine will get 3% better economy than the V8 it replaces, so that means about 24-25 mpg city, 15-16 mpg highway, 19 mpg combined in the EPA driving cycles in the gasoline-online version.
-- The electric motor adds 20 hp and 155 pound-feet of torque, and the nice thing about electric motors is that they produce maximum torque at low rpm.
-- The transmission unit houses both the gearbox and the electric motor. There is no starter motor; its place is taken by the electric motor.
-- Batteries are lithium-ion, not nickel-metal hydride, and they don't take up any trunk space, unlike many other hybrids.
-- BMW says the hybrid will be about 15% more efficient, which suggests 28-29 mpg in city driving.
-- BMW hasn't released performance claims yet but the gasoline-engine car does 0-100 kph (0-62 mph) in 6.2 seconds, so it's possible the hybrid would break 6 seconds. Not that anyone would ever use a hybrid car to go fast.

This is a mild hybrid, meaning both powerplants are engaged together, but not the electric motor only. It will regnerate power under decleration and will shut off at stoplights. The strong hybrid technology (also called full hybrid or active hybrid), which allows a car to start off on electric power alone, may appeal more to purists, but it doesn't necessarily translate to better real-world fuel economy. The mild hybrid will certainly be less annoying to those caught behind a strong hybrid. Some Prius owners delight in seeing how many tenths of a mile they can travel from a stoplight before the gasoline engine kicks in, oblivious to the traffic backed up behind them.

The most likely competition for this car isn't hybrids such as the Toyota Prius or Nissan Altima, but high-end cars such as the Mercedes-Benz S-Class. Mercedes has its own hybrid prototype, the S400, and the hybrid drivetrain is jointly developed with BMW to cut costs and speed time to market. The engines and bodies are completely different, however.