Technology changes related to EPA's 2010 emissions standards for heavy-duty trucks are causing an increase in engine problems and a decrease in overall satisfaction with the powertrain, according to the J.D. Power and Associates' 2012 U.S. Heavy-Duty Truck Engine and Transmission Study.

Now in its 16th year, the study measures satisfaction with engines and transmissions among primary maintainers of heavy-duty (Class 8) trucks that are one model-year old. Satisfaction is measured based on eight key factors:
- engine reliability and dependability
- engine warranty
- acceleration when fully loaded
- electronic control module
- accessibility to components for service or maintenance
- vibration at idle
- maintaining speeds on grades
- average fuel economy.

The study finds that 46% of owners of heavy-duty trucks that are one model-year old report experiencing some type of engine-related problem, up from 42% in 2011. The most commonly reported engine problems are issues with the electronic control module calibration (cited by 23% of owners who experienced an engine problem), exhaust gas recirculation valve (20%), and electronic engine sensors (16%).

In addition, the average number of engine- and fuel-related problems has increased to 81 problems per 100 vehicles (PP100) from 71 in 2011. The rise in problems has affected overall engine satisfaction, which dropped to 719 index points on a 1,000-point scale in 2012, compared with 739 in 2011.

"At the industry level, the new, more complex engines designed to meet EPA regulations are resulting in additional problems and downtime, which also has a financial impact on owners because they're not making money when their truck is down for service," said Brent Gruber, director of the commercial vehicle practice at J.D. Power.

However, Gruber adds that once manufacturers resolve quality issues related to the new technology, customers may expect to see some added benefits from the new engines. In the on-highway segment, the average reported engine service interval has increased to 22,703 miles in 2012, up from 20,303 in 2011. Additionally, maintainers of heavy-duty on-highway trucks report a 4% increase in fuel efficiency this year, averaging 6.3 mpg in 2012, compared with 6.0 mpg in 2011.

"The new engines are proving to be more fuel efficient and allowing greater up-time between service, so despite initial quality issues, the new technology may offer a greater return on investment in the long run," said Gruber.

Detroit engines ranked highest in customer satisfaction with a score of 753 (a 20-point improvement from 2011) and performed particularly well in the engine reliability and dependability factor. Cummins ranked second at 729 and Caterpillar third at 721.

Overall satisfaction with heavy-duty truck transmissions averaged 812 in 2012, down eight points from 2011.

The decline is largely attributed to lower satisfaction with the reliability and dependability of the transmission and drivetrain. This decline in satisfaction comes despite transmission-related quality actually improving to 7 PP100 in 2012, down from 10 PP100 in 2011.

The 2012 U.S. Heavy-Duty Truck Engine and Transmission Study is based on the responses of 1,725 primary maintainers of Class 8 heavy-duty trucks that are one model-year-old. The study was fielded between February and May 2012.