VW Details 42-mpg Passat Sedan Powertrain

Volkswagen AG says it can hike the U.S. highway fuel economy rating of its Passat sedan 31% to 42 mpg with a combination of turbocharging, cylinder deactivation and automatic stop-start systems.

VW will present the result as the Passat BlueMotion concept next week at the Detroit auto show.

The car is equipped with a new version of VW's 1.4-liter direct-injection turbocharged gasoline engine that makes 150 hp and 184 lb-ft of torque. The $21,000 base U.S. version of the 2014 Passat is powered by a 2.5-liter, 5-cylinder turbocharged engine rated at 170 hp, 177 lb-ft of torque and 32 mpg on the highway.

The BlueMotion concept's engine is fitted with a system VW already offers in Europe that can deactivate two of the four cylinders under low-load conditions.

Other fuel-saving features include VW's European stop-start system that shuts off the engine during temporary stops and a coasting device that uncouples the engine from the transmission when the driver releases the accelerator.

VW hasn't said when it might offer the concept's powertrain in the American market. But the company hints that the system will be needed to meet future U.S. fuel economy standards.