Expectations play a big role in the minds of luxury car buyers. That means a turbocharged four-cylinder might take some explaining in a $57,275 BMW 528i.

At the heart of it, it's not the number of cylinders that matters, but rather how they all behave. For the most part, the 240-hp, 2.0-liter turbocharged four-cylinder provides satisfying performance. This is a rather heavy car, yet it doesn't feel underpowered. Acceleration is brisk, living up to the image of the BMW roundel on the hood. As expected, fuel economy is impressive. We didn't run the full array of measured fuel economy tests on this borrowed press car from BMW, but I saw a solid 26 mpg in my commute.

This is the fourth BMW we've driven with this engine: we own a 328i, Z4, and X3 with the same powerplant. Maybe it's no surprise that noise, vibration, and harshness is better suppressed in its larger applications, like the X3 and this 528i. Driving along with the windows up and the radio on, engine noise and vibration are very well muted.

This doesn't mean that you wouldn't notice the difference between the turbo four and the 3.0-liter inline six-cylinder it replaced. You wanted to listen to the sweet-sounding inline six as it revs through the gears, totally the opposite approach from the 528i's almost-silenced four-cylinder. The eight-speed automatic is very smooth, but it shifts quite frequently to keep things on boil. There is also some brief hesitation pulling into intersections or downshifting promptly to squirt into a hole in traffic when merging.

Unfortunately, low-speed driving with the windows down or standing outside of the car with the engine running shatters the veneer of luxury - unless your definition of luxury includes diesel-like engine noise. Direct-injection clatter makes this gasoline engine sound more like a diesel than some actual passenger car diesels. All in all, Ford did a better job of isolating and refining their 240-hp, 2.0-liter turbo four in the Edge, Explorer, and Taurus.

Finally, like the other BMWs with this engine, the 528i has a start-stop system that saves about one mpg in city driving by shutting the engine off when stopped, like at a traffic light or in stop-and-go traffic. Unfortunately, the restart isn't refined, sending a shudder through the seat. Hybrids and some other gas-only cars do this better.

Otherwise the 528i drove a lot like the 535i we previously tested. This well-equipped press car has the optional sports package. It improves the steering somewhat but still falls short of the feedback we loved in earlier BMWs. We like the optional multi-contour seats that also come with the sports package; they provide better lateral support without feeling confining. The interior is very plush and quiet. The iDrive control system remains a frustration but has some advantages, like real-live climate buttons, over newer rival touch-screen systems.

Overall, we think the 528i almost achieves its goals of combining fuel efficiency and luxury. And according to BMW, at least, their customers don't seem to mind the few sacrifices. We'll see more automakers going this route as fuel-economy standards progressively become more stringent.