DETROIT – Honda unwraps a more fuel-efficient and roomier third-generation Fit subcompact today at the 2014 North American International Auto Show.

The ’15 Fit, on sale in the U.S. in spring, replaces the current model introduced in the U.S. in fall 2008.

Despite that car’s advanced age, sales of the Fit grew 8.4% last year, although its 53,513-unit total was less than half the volume of the segment-leading Nissan Versa, WardsAuto data shows.

Honda says the new Fit will be the most fuel-efficient B-car in its segment in the U.S., with combined fuel economy projected to hit 36 mpg (6.5 L/100 km), up steeply from a maximum of 31 mpg (7.6 L/100 km) in the ’14 model. Currently, the ’14 Versa Note with a continuously variable transmission and 35 mpg (6.7 L/100 km) combined holds the title.

The key to the improved fuel economy, Honda says, is the U.S. debut of its 1.5L direct-injected DOHC 4-cyl. engine, making 130 hp and 114 lb.-ft. (155 Nm) of torque. The ’14 Fit makes 117 hp and 106 lb.-ft. (144 Nm) of torque from its non-DI 1.5L 4-cyl.

Other than the CVT, which has optional paddle shifters, buyers of the ’15 Fit can opt for a 6-speed manual transmission.

For ’15, ride comfort has been improved and noise, vibration and harshness levels are reduced, thanks to new rear dampers and a revised suspension geometry.

The new Fit employs more ultra-high-tensile strength steel for a more rigid body. The increased use of lighter-weight steel reduces the car’s underbody and chassis weight by 57 lbs. (26 kg), Honda says. Further, the automaker expects top crash scores from NHTSA and the Insurance Institute for Highway Safety, including a “good” rating in IIHS’ stringent small-overlap barrier test, which mimics a collision with a narrow pole.

The car loses 1.6 ins. (4.1 cm) in total length but gains 1.2 ins. (3.0 cm) in wheelbase from ’14.

Despite the relatively small change in exterior dimensions, the car’s passenger space grows sharply, up 4.9 cu.-ft. (0.1 cu.-m) with 4.8 ins. (12.2 cm) more rear legroom than its predecessor.

Cargo volume, although down substantially with the seats folded, still is more than any other model in the class offers, Honda claims.

The Japanese automaker promises an “above-class” interior in the ’15 Fit’s cabin, with soft-touch materials and, for the first time in the car, optional leather seating.

Standard on the ’15 subcompact will be Bluetooth, a multi-angle rearview camera and Honda’s Expanded View driver’s mirror.

Available features include heated seats and side mirrors, push-button start and a 7-in. (17.8-cm) touchscreen with HondaLink smartphone connectivity.

The new-generation Fit marks the first time Honda will assemble the car in North America, with production set to get under way in February at its new Celaya, Mexico, plant. Celaya has a 200,000-unit annual capacity and also is set to build a small CUV off the Fit platform later this year.

cschweinsberg@wardsauto.com