Photo Courtesy of Ford Motor Co.

As it expands its V-6 engine lineup on the 2015 F-150 pickup, Ford will have only one V-8 option next year. Sales of the smaller engines will account for more than 70% of F-150s, Ford predicts.

In an unexpected twist of economics, a V-6 pickup can now cost more to buy than one equipped with a larger V-8 engine. Such is the case with the 2014 Ram 1500 Tradesman, whose prices start at $24,610 when equipped with a standard 3.6-liter V-6 engine. Specify an optional 5.7-liter V-8 HEMI and the price drops by $640.

Traditionally, pickup-truck buyers viewed a V-8 engine—not a V-6—as the premium choice. However, national fuel costs flirting with $4 per gallon and a federal mandate for automakers to achieve an average fuel economy of 54.5 miles per gallon by 2025 have truck makers offering more fuel-efficient V-6 engines. Fleet owners stand to save operating costs from the broader power choices but will need to match trucks carefully to the desired application, suppliers advise.

For truck owners that rarely tow or haul heavy loads, a beefy V-8 may now be overkill. "If you need all the capability that the V-8 delivers from a towing and payload standpoint, we've got that," says Bob Hegbloom, director of the Ram brand. "The flip side is that you're going to have individuals who don't need it."

A fuel-efficient transmission is the reason behind Ram's slight price uptick on the Tradesman. The eight-speed gearbox comes with Ram's V-6, offering 25 mpg on highway; bolted to a transmission with two fewer gears, the V-8 gets just 22. Ram predicts V-6 engines—including its new 3.0-liter EcoDiesel, which reaches 28 mpg on the highway—will cover around 30% of its half-ton-pickup sales next year.

As it prepares to roll out its aluminum-bodied 2015 F-150 pickup, Ford Motor Co. expects V-6 engines will comprise more than 70% of all F-150 sales. Ford's 3.5-liter V-6 EcoBoost engine already has surpassed its 5.0-liter V-8 as the truck's most popular power choice, capturing 47% of F-150 sales. While early skeptics pointed to the engine's twin turbochargers as a potential weak link that would require costly repairs, more than 500,000 F-150s have been sold with the boosted V-6, rated at 22 mpg on the highway.

"We have a lot of fleet customers that have EcoBoost engines in service," says Doug Scott, Ford truck-group marketing manager. "As time goes on, we continue to prove out just how durable these EcoBoost engines are." Next year, Ford will add to the mix an even smaller turbocharged V-6, with just 2.7 liters. The 5.0-liter engine will stay on as the truck's only V-8 power choice, while a naturally aspirated, 3.5-liter V-6 will replace the current 3.7-liter base engine. The truck's lighter aluminum body allows Ford to offer smaller engines but still maintain an effective power-to-weight ratio, it says.

Traditionally, the base V-6 was the top pick among fleet buyers, especially those not needing to tow or haul frequently. Ford says its new V-6 engine lineup will allow fleets to buy a truck better suited to occasional hauling without spending extra money at the pump filling a thirstier V-8.

"I think we'll be opening up the whole fleet market with this 2.7 EcoBoost," says Scott, who notes that it will have a lower acquisition price and better fuel economy than the 3.5-liter. Ford has not yet disclosed specific power, torque or fuel economy ratings for the 2015 F-150.

General Motors, too, sees growth in the V-6 pickup segment, noting that they now account for about 20% of its 2014 Chevrolet Silverado and GMC Sierra light-duty pickups, up from 5% for the prior model. The truck maker offers just one V-6 engine: a 4.3-liter that gets up to 24 mpg on the highway.

"Fleet customers are just thrilled with it," says Tom Wilkinson, Chevy truck spokesman. The V-6 engine, which was redesigned for the latest truck model, uses direct injection, variable valve timing and cylinder deactivation to save fuel.

Wimpy horsepower and torque, with unimpressive fuel economy, used to be the drawback of past V-6 engines. This is not the case today, as Chevy's 4.3-liter V-6 produces 285 hp and 305 lb-ft of torque and Ram's 3.6-liter V-6 hits 305 hp and 269 lb-ft of torque. Ford's 3.7-liter V-6 grinds out 302 hp and 278 lb-ft of torque, while its 3.5-liter Ecoboost soars to 365 hp and 420 lb-ft of torque.

Today's V-6 pickups "are putting out what would have been mainstream V-8s 10 years ago," Wilkinson says.