Heavy-duty truck engine quality has improved from 2010, after technology changes related to emissions standards revisions caused a spike in engine-related problems during recent years, according to the J.D. Power and Associates 2011 U.S. Heavy-Duty Truck Engine and Transmission Study.

Now in its 14th year, the study measures satisfaction among primary maintainers with engines and transmissions in heavy-duty 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; and average fuel economy.

The 2011 study finds that 42% of owners of heavy-duty truck engines that are one model-year old report experiencing some type of engine-related problem, down from 46% in 2010. However, this is still well above the historically low average in 2004, when 26% of owners of truck engines that were two model-years old reported experiencing a problem.

The low problem incidence level occurred prior to implementation of two rounds of emissions standards revisions.

The most-commonly reported engine problems are issues with the exhaust gas recirculation valve, 23% or owners, and electronic control module calibration, 21%.

Also in 2011, engine problems have decreased to an average of 66 problems per 100 vehicles from 72 PP100 in 2010. As a result, satisfaction with engines has increased by 22 points to an average of 739, on a 1,000-point scale.

"It's encouraging to see that the number and frequency of problems is improving," said Brent Gruber, senior manager of the commercial vehicle practice at J.D. Power and Associates. "With the new technology required to meet emissions standards, today's engines simply are more problematic than the previous generation."

Gruber notes that the most recent emissions standards revision took place in 2010. How those changes will affect quality and customer satisfaction will be reflected in the 2012 J.D. Power study.

"Given the quality issues that arose from new emissions requirements in 2004 and 2007, the 2010 emissions standards will likely create another round of challenges for engine manufacturers," said Gruber. "The manufacturers that best handle the integration of these new standards will have a distinct competitive advantage."

Upcoming emissions and fuel efficiency standards recently announced by the U.S. government will put additional pressure on engine manufacturers for the next several years, Gruber added.

"Although engine manufacturers are facing yet another mandate, we expect that the change in improved fuel efficiency will result in higher satisfaction and loyalty for the engine brands."

The study finds that, among owners who report average fuel consumption of 5.0 to 5.9 mpg, satisfaction with fuel economy averages 5.9 on a 10-point scale. In addition, 58% of these owners said they "definitely will" or "probably will" specify the same engine brand in their next heavy-duty truck.

Among owners who report an average fuel consumption of 6 mpg or more, satisfaction with fuel economy increases to 7.1 and intended engine loyalty increases to 66%.

Navistar's International MaxxForce engines ranked highest in customer satisfaction with a score of 760 and performed particularly well in four of eight factors in the survey: engine reliability and dependability, engine warranty, vibration at idle and average fuel economy.

The 2011 U.S. Heavy-Duty Truck Engine and Transmission Study is based on the responses of 1,651 primary maintainers of Class 8 heavy-duty trucks that are one model-year-old. The study was fielded between February and May 2011.