Until recently, the only market segment in the United States that had embraced diesel engines was heavy duty pickup trucks. While we were in Maryland this week to drive the 2011 General Motors HD pickup trucks powered by the revised 6.6-liter Duramax diesel V8, we took the opportunity to ask about the now-shelved 4.5-liter diesel. Like Ford and Chrysler, GM was planning to launch diesel engines in its light-duty pickups this year until the economy – and sales – went in the tank.

The Ford 4.4-liter V8 will live on in the 2011 Range Rover and, while there are no current production plans for the 4.5-liter Duramax, many of the prototypes are still running. According to GM sources, a fleet of the diesel 1/2-ton trucks are still being used on a regular basis by GM engineers.

The Duramax was apparently delivering great performance with towing and payload capabilities well beyond those possible with the two-mode hybrid pickup trucks. Even more importantly, the diesel Silverado was on track to achieve combined fuel economy of 25 miles per gallon, compared to the 22 mpg combined rating of the hybrid. At the time the program was put on the shelf, ninety percent of the production tooling was ready to go and it seems a shame that we'll probably never get a chance to drive this engine.

[Source: General Motors]