The 528i, 535i and 550i are rated at 240, 300 and 400 horsepower, respectively. The turbocharged version of the 3.0-liter inline-six-cylinder in the 535i makes the 550i superfluous, rocketing the car to 60 mph in less than 6 seconds. If you prefer 5 seconds, the 550i's twin-turbo 4.4-liter V-8 will deliver, but the 535i's character is more than you might expect from a turbo-six. There was some hesitation at times, but I wouldn't attribute it to turbo lag, because it's intermittent. Almost across the board, this turbo-six feels like a V-8. It's damn impressive, and plenty efficient at 20/30 mpg city/highway with the automatic transmission. This beats practically all competitors. Only the base Audi A6 tops it, at an estimated 21/30 mpg.

All-wheel drive, in the 535i xDrive, gives up 1 mpg. The six-speed manual transmission, available only with rear-wheel drive — is rated lower still, at 19/28 mpg. The 528i, which comes only with an automatic and rear-wheel drive, saves you a couple of mpg, rated 22/32 mpg. The 550i's best performance is 17/25 mpg with the automatic, 16/24 mpg with xDrive and 15/22 mpg with the manual transmission. All the cars require premium gas.

Where does this efficiency come from? Direct fuel injection plays a part, but as the mileage ratings reflect, the new eight-speed automatic transmission is a major player. My impressions of it are positive overall, though it's more effective with the 550i's larger engine (as is often true of automatics). What stood out was how quickly it kicked down under all circumstances, be it one gear, three gears, basically anything. This isn't always the case. In fact, historically, an increase in the number of a transmission's gears hasn't always guaranteed satisfying performance.

The transmission's responsiveness was still good in the 535i, but it wasn't quite as quick and decisive on the downshift as it had been in the 550i. In either car, sliding the gear selector to the left (the only position it actually stays in) activates an automatic Sport mode, which raises the rpm at which the transmission upshifts. It's a sportier approach, but it doesn't seem to speed the actual gear-change time. You can also shift manually by then pushing the stick forward or back, or by using paddles on the steering wheel. Frankly, with eight speeds to work with, you're always wondering what gear you're in, where you need to be and if it will even let you shift higher or lower from your current speed. The fun is lost.

Automatics have become so smooth that you often can't tell when they're shifting up. In normal Drive mode in the 535i, I was quite aware of the shifting. It's under heavier acceleration that the transmission is its smoothest. It's an odd approach, but we don't object.