Study reports engine problems in emission-controlled diesel engines

9 October 2006

As manufacturers of heavy-duty truck engines are implementing new emission technologies to meet diesel emission standards, customers are increasingly experiencing problems with their engines, according to the 2006 edition of the Heavy-Duty Truck Engine/Transmission Study by J.D. Power and Associates.

The study measures customer satisfaction with the engines in two-year-old heavy-duty trucks (Class 8) by examining four vital engine factors. They are (in order of importance): engine quality (30%); engine performance (26%); engine cost of ownership (22%); and engine warranty (22%). The study examines engines supplied in 2004 model-year trucks, the second model year impacted by the Consent Decree, and the first model year to fully comply with the EPA 2004 emission standards.

To meet the more stringent NOx emission requirements, manufacturers had to redesign their engines and employ new technologies, such as the exhaust gas recirculation (EGR). As a result, the average number of reported engine problems has increased to 74 PP100 (engine problems per 100 vehicles), up from 46 PP100 in 2005, concluded the study.

Whenever a new technology is employed, it takes time to fine tune the new design. As time goes on and engines are better equipped and designed to follow the emission standards, the number of problems should gradually decline, noted J.D. Power.

For the sixth year, a Caterpillar engine ranked highest in the vocational segment. Vocational trucks are defined as those with body types used in rugged job applications, such as dump trucks, concrete mixers, and garbage/refuse recycling trucks. The Caterpillar C-12 ranked highest among vocational heavy-duty truck engine models, performing particularly well in three of the four factors that determine overall satisfaction: engine quality, performance and cost of ownership. The Caterpillar C-15 followed the C-12 in the rankings.

The study also found that among the four drivers of engine satisfaction, customers were least satisfied with the cost of ownership, particularly in the areas of routine engine maintenance costs and fuel efficiency. Reported fuel consumption for heavy-duty engines has declined to 5.72 mpg in 2006, down from 5.91 mpg in 2005 and 6.04 mpg in 2004.

Source: J.D. Power