GM revamping Diesels to meet new emission standards.
GM says reworking the 6.6-liter diesel, which powers heavy-duty versions of the Chevrolet Silverado and GMC Sierra pickups, won't interrupt production. But the modifications are expected to sharply increase the cost of building the engine. Heavy-duty trucks with a gross vehicle weight rating of as much as 10,000 pounds must meet the Tier 2 Bin 5 emissions standards. The new rules call for a 90 percent reduction of oxides of nitrogen, or NOx, and particulate matter, or soot.