Kenworth and Hino topped J.D. Power and Associates' 2010 U.S. Medium-Duty Truck Customer Satisfaction Study. The research firm also reported that overall service satisfaction among truck owners declines considerably if their trucks are not ready when promised.

Kenworth ranks highest in customer satisfaction with dealer service while Hino ranks highest in customer satisfaction within the conventional truck segment, the survey found.

Hino's score of 815 out of a possible 1,000 was highest in customer satisfaction within the conventional truck segment. Hino performed well across all factors -- driving satisfaction, engine satisfaction, and overall quality. Ford (770) and Peterbilt (760) follow in the product rankings.

Kenworth's customer service score was 812, and it did particularly well in the dealer facility factor. Ford follows in the rankings with 808 points.

The study also found that Class 5 trucks have the highest quality levels among medium-duty vehicles, with a score of 105 problems per 100 trucks (PP100). In comparison, Class 6 trucks average 140 PP100, and Class 7 trucks average 131 PP100.

"The larger trucks -- Class 6 and 7 models -- tend to be more sophisticated and are used for more demanding applications," said Todd Markusic, senior director of the commercial vehicle practice at J.D. Power. "The greater weight and the more rugged use of these trucks have an adverse effect on quality. Quite simply, there is more that can go wrong."

The study found that overall service satisfaction averages 215 points higher (on a 1,000-point scale) among truck owners who receive their truck when promised, compared with those who do not.

"Clearly, the message to dealers is to avoid over-promising when the truck will be ready, given that not meeting the deadline will greatly detract from the service experience," Markusic said. "The key is managing expectations. Even for repairs that take longer than normal, if they are done within the timeline that was initially provided to the customer, dealers can achieve high levels of service satisfaction."

The study also found that engine- or fuel-related problems typically result in the greatest amount of downtime. A truck with an engine or a fuel problem averages eight days of downtime.

"Given that the average annual downtime for a truck is six days, manufacturers who have the fewest engine and fuel issues can have a real competitive advantage due to minimizing the time the truck is out of commission," said Markusic.

The study, now in its 18th year, measures customer perceptions of 2009 model-year Class 5, 6 and 7 commercial trucks. Within the product segment, six factors are used to determine overall satisfaction: warranty; engine; cost of operation; ride/handling/braking; cab and body; and transmission.

The study also measures satisfaction with services received from an authorized truck dealer: dealer facility; service quality, service delivery; service advisor, service initiation; and price.

The 2010 U.S. Medium-Duty Truck Customer Satisfaction Study is based on responses from 1,258 primary maintainers of 2009 model-year Class 5, 6 and 7 conventional cab medium-duty trucks. The study was fielded between June and July 2010.