The Duramax Diesel is offered in this new Chevrolet Silverado HD model pitched during last weekend's Super Bowl.

General Motors and its Japanese partner Isuzu are betting on a surge in demand for heavy-duty diesels, announcing plans to invest $50 million in a plant in Ohio – a move they say will “protect” 500 jobs.

The investment appears to reflect a growing interest in diesels in a market that has long been skeptical of the high-mileage technology. But a growing number of competitors, including Chrysler and Nissan, have either added or plan to expand their diesel offerings for full-size and heavy-duty trucks.

“Today’s announcement demonstrates GM’s commitment to continuously invest in technologies that reduce the impact of our vehicles on the environment, while maintaining performance attributes required by customers in the areas of towing and hauling loads,” said GM North America Manufacturing Manager Christine Sitek.

Known as DMAX, Ltd., the facility in Moraine, Ohio has produced about 1.6 million diesel engines since opening in 2000.  It currently assembles the Duramax 6.6-liter Turbo Diesel engine used in the Chevrolet Silverado and GMC Sierra pickups, as well as the Chevrolet Express and GMC Savana full-size vans.

(BMW introducing new 7-Series diesel at Chicago Auto Show. Click Here for the story.)

GM isn’t saying precisely what sort of changes will be made as a result of the latest investment, though it notes that the joint venture has received $760 million in upgrades since 2000.

Today’s market for diesels has changed dramatically since the beginning of the millennium.  Buyers expect even more from their engines today, not only better fuel economy and extended durability, but also in terms of quietness, smoother ride and increased towing and hauling capabilities.

Mileage, however, has become a real competitive factor in the truck market and diesels have a significant advantage here.  Chrysler’s new Ram 1500 EcoDiesel, for example, was just named the most fuel-efficient full-size truck in the market by the EPA with a highway rating of 28 mpg.

(Click Here for more on the Ram diesel.)

But Ford may soon topple the new king-of-the-hill with its 2015 “aluminum-intensive” F-150.  By shedding as much as 700 pounds in mass, Ford is expected to reach as 30 mpg with one or more versions of the truck.

GM isn’t expected to follow the “lightweighting” approach – at least not until the most recently introduced generation of Chevy and GMC pickups reach the end of their lifecycle, so coming up with an even more efficient diesel may prove critical to keeping the Silverado and Sierra models competitive, analysts suggest.

The Duramax diesel already uses some of the more advanced technologies available for oil burners, however, including super-high-pressure fuel rails and piezoelectric injectors.

But diesels are facing increasing challenges, notably the planned ramp-up of federal emissions guidelines.

“The Duramax diesel’s performance is renowned in the industry, and these updates to improve our emissions will make it that much better,” said Maho Mitsuya, DMAX president and chief operating officer.

GM holds a 60% stake in the DMAX joint venture, Isuzu a 40% share.  The two companies have had a series of ongoing alliances dating back for decades.

(Mazda again delays launch of SkyActiv-D diesel. Click Here to find out why.)