Lexus vehicles like the GS sedan once again dominated the Power measure of dealer service.

Sure, those car dealers are easy to poke fun at. But a new study suggests American motorists are more than happy, on the whole, with the service they’re delivering.

For the fifth year in a row, Lexus led the closely watched J.D. Power Customer Service Index, a measure of how well are meeting owners’ expectations for performance at their repair shops. Detroit-based GMC, meanwhile, jumped into the lead among mass-market brands, according to the market research firm.

The annual CSI found that customers are becoming increasingly satisfied by dealer service in general, especially with the service they get from factory-approved retailers as compared with independent facilities.

“Manufacturers have made large investments in their retail programs, and dealers have made significant investments in key customer touch-points—people, improved processes and customer waiting areas—which are having a profoundly positive impact on their customers,” said Chris Sutton, the JDPA senior director in charge of the 2013 survey.

The CSI focuses on what happens when vehicle owners visit a service department for either maintenance and repair work asking about five specific areas:  service quality, service initiation, service advisor, service facility and vehicle pick-up.

While dealer service departments and independent repair outlets may be a traditional source of suspicion and complaints, the results of the latest survey indicate a big improvement in recent years. The average score was 797, on a 1,000-point scale, up from 787 last year, and a 29-point gain from 2011.

Significantly, owners said they were generally more satisfied with the service they got from facilities affiliated with one of the major automakers rather than from independent service facilities.

On average, the owners who participated in the CSI study visited a dealer service department an average 2.6 times a year, the vast majority of the time for maintenance rather than for repairs.

Overall satisfaction was particularly high among those motorists getting routine maintenance. That suggests the auto industry is making inroads as it shifts focus from traditional repair business. With today’s cars boasting better quality and reliability than ever before, more and more dealers are emphasizing such things as oil changes or tire rotation to keep their mechanics busy and the cash registers ringing.

Perhaps reflecting some belt-tightening as the economy continues to struggle, the 2013 CSI found that customers spent less out-of-pocket during visits to the repair shop, an average $118 compared to $125 the prior year. That could also reflect the fact that many makers have been adding routine maintenance to their traditional warranty coverage.

Satisfying customers has a number of advantages.   It not only generates more revenue but increases customer loyalty, according to JDPA Director Sutton. Among CSI survey participants, in general, 38% said they “definitely will” buy a vehicle from the same brand when it’s time to trade in.  That jumped to 59% among customers who said they were “delighted” by the service delivered by their dealers.

“The service experience has a profound impact on vehicle owners, not just where they take their vehicle the next time they need maintenance or repairs, but also on their next vehicle purchase,” said Sutton. “Dealers know this, and most are taking the appropriate steps to ensure their customers have the best experience possible on both the sales and service sides of the store.”

Toyota’s luxury brand Lexus maintained its winning streak in the 2013 CSI with a score of 862. Cadillac was a close second, at 858 points, followed by Jaguar, Acura and Infiniti.  Notably, were Hyundai to sell its Equus models as an independent brand – which it once considered – the model would have outscored Lexus.

Three of the 11 luxury brands improved their scores by at least 20 points. So did five of the mainstream marques.

Among mass market brands, GMC landed a score of 819, followed by Mini, Buick, Chevrolet and Volkswagen.

A total of 91,000 owners of 2008 through 2012 model-year vehicles participated in the study.