2008 BMW 135i Convertible

The BMW 1-series, available as a coupe and a convertible, seems poised to be a very exciting addition to the company's lineup. The 1-series uses the same, highly regarded mechanicals as the benchmark 3-series, but wraps them in a smaller, lighter, and less expensive package. From a driving standpoint, one can hardly argue with the results. But what is open to debate is whether the cost and weight savings of the 1-series are significant or does the car too closely overlap to the 3-series.

A glance at the window sticker for our 135i convertible certainly suggests the latter. The bottom-line number of $48,445 sure sounds like 3-series money. It is in fact very close. The 335i convertible starts at $50,400, and it comes with a retractable metal hardtop, as opposed to the 135i's fabric roof. The 328i convertible starts at $44,300.

To be fair, our test car was larded with options. The premium package (power seats and a bunch of minor items) was a whopping $3300; the six-speed automatic was $1275; the sport package (seats, steering wheel with shift paddles, eighteen-inch wheels, performance tires, and Shadowline trim) added another $1100; additional items (heated seats, iPod adapter, HD radio, satellite radio, and rear parking aid, among others) pushed the price up by $2895 more.

If the 135i isn't far from the 335i in price, the two models are largely identical mechanically. Both use the same 3.0-liter turbocharged straight six and (optional) six-speed automatic. The super-sweet engine seamlessly integrates its two turbochargers, creating a stepless wave of power as the revs climb. Peak output is 300 horsepower and 300 pound-feet of torque. It wasn't long ago that those were M3 numbers. In the 335i, they're enough for a 0-to-60 mph run of 5.7 seconds, whereas the lighter (by 286 pounds) 135i does it in 5.5 seconds. Both cars have the same EPA ratings, 17 mpg city and 26 mpg highway. The automatic wouldn't be our preference - the slick manual is more rewarding from both a tactile and a financial standpoint - but we couldn't fault its logic and its response is instaneous.

The 135i is more than eight inches shorter than the 3-series, and the stretch between the axles is trimmed by four inches exactly. Both convertibles are strictly four-seaters, and both require the cooperation of front-seat occupants (moving their seats up) in order to accommodate adults in back. In fact, their factory-measured rear-seat legroom figures are within an inch of each other. Similarly, their trunk-space measurements are very close as well, with the 3-series having a slight edge when the top is up, but the 1-series winning out when their lowered, as its fabric roof stows more compactly than the 3-series's retractable hardtop.