The number of new mid-size pickup trucks has dwindled in recent years, leaving many analysts to wonder what might have been.

The speculation will end soon, because a new pair of mid-size trucks is finally nearing showrooms--and in due course, they will offer a high fuel-efficiency diesel engine as an option.

The launch of the 2015 Chevrolet Colorado and 2015 GMC Canyon pickups is just a few months away, and General Motors is expecting these small trucks to have a big impact on the market.

Speaking to WardsAuto, Chevy and GMC marketing managers were confident that the new mid-size trucks would win back customers who have switched to other vehicles as the segment has dwindled.

2015 Chevrolet Colorado Z71

2015 Chevrolet Colorado Z71

The previous-generation Colorado and Canyon departed showrooms in 2012, following the discontinuation of the Ford Ranger and Ram Dakota.

That's left the aging Nissan Frontier and Toyota Tacoma as the only major players.

With fewer choices available, many buyers switched to full-size pickups and crossovers, GM says, but the company believes these customers' needs haven't really changed, and can still be best served by a small truck.

GM hopes to lure those customers back with modern designs and more-efficient powertrains.

At launch, base Colorado and Canyon models will come standard with a 2.5-liter four-cylinder gasoline engine, producing 200 horsepower and 191 pound-feet of torque. An optional 3.6-liter V-6 will be good for 305 hp and 269 lb-ft.

2015 GMC Canyon

2015 GMC Canyon

Buyers will be able to choose between rear-wheel drive and four-wheel drive. A six-speed manual transmission will be offered on business-focused Work Truck models with rear-wheel drive; the rest will get a six-speed automatic.

By late 2015, the Colorado at least will also get a diesel engine option. The 2.8-liter Duramax four-cylinder will make it the smallest diesel truck on the market.

The only diesel alternatives are the full-size 2014 Ram 1500 EcoDiesel and upcoming Nissan Titan, or even larger heavy-duty trucks. That should make the Chevy appealing to buyers who don't need such a large vehicle to meet their needs.

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