Diesel engines get better gas mileage than gas engines. Hybrid powertrains (combining a battery, electric motor and combustion motor) more efficiently utilizes energy than traditional powertrains. I’ve pointed out in the past there would be a big benefit to combining a diesel engine with a hybrid powertrain. Apparently Wal-Mart thinks so too:
“Wal-Mart, the largest US retailer, is to work with ArvinMeritor, the auto component supplier, on the development of a diesel-electric hybrid truck, as part of its new focus on improving its environmental performance. The companies said in a statement they had agreed to develop a dual-mode, diesel-electric drivetrain for a Class 8 truck tractor truck - the workhorse of the US long-distance trucking industry.”