Diesel engines are common in heavy-duty pickups but have not been available in light-duty models since the late 1970s. Why the long break? Diesel engines looked good when fuel prices were high following the energy crisis—and automakers were beginning to put them in cars and light-duty trucks. But an oil glut in the 1980s lowered the cost of fuel to the point where it didn't make sense to spend more for a diesel engine.
According to an article on edmondson.com manufacturers say they didn't revisit diesel because traditional designs were too heavy to work well in a light-duty chassis and because stricter emissions requirements for mass-market half-ton trucks made it hard to use that type of engine. The author of that story theorizes that it may also be because car companies did not want to lose sales of pricey heavy-duty trucks by offering cheaper diesel models.
The economics and technology are different now, which is why Chrysler is introducing the 2014 Ram 1500 EcoDiesel Pickup. Fuel prices are high and likely to remain that way because of demand by China and other developing countries—so there's an economic argument to be made in favor of diesel. And the technology has improved to the point where it's possible to meet strict emissions standards with diesel engines.
The Ram 1500 EcoDiesel pickup will have a 3.0 liter engine capable of producing 240 HP and 420 pound-feet of torque. It has a tow rating of 9,200 pounds. For more on this new vehicle see the fun and informative video review below.