The biggest diesel trucks on the road have taken a "precipitous drop" in reliability as vehicle manufacturers have incorporated new emissions controls required by the U.S. Environmental Protection Agency, says one expert at J.D. Power and Associates.
In two separate studies this summer, J.D. Power surveyed fleet managers in the heavy-freight and vocational, or work truck, vehicle categories. The studies cover Class 8 trucks and engines for the 2011 model year, which was the first full year that the latest round of clean diesels were shipped to customers.