The service departments for Lexus, Buick and Cadillac dealers do the best job of catering to their customers' needs, according to the J.D. Power and Associates 2006 Customer Service Index Study released Thursday.

Volkswagen and Isuzu owners aren't nearly as impressed, the study says.

Lexus ranks highest with an overall CSI score of 912 points on a 1,000-point scale. It moved up from the fourth spot in last year's survey to edge out Lincoln, which has held the No. 1 spot for the last two years. Lincoln was fifth this year with a score of 906.

Buick ranks second with a score of 911, followed by Cadillac with 909.

Isuzu earns the worst score for the second year in a row with 781 points. Volkswagen (810) and Suzuki (823) are not far behind.

The customer satisfaction survey is based on six areas of service: service initiation, service adviser, in-dealership experience, service delivery, service quality and user-friendly service.

The research firm collected responses from 79,580 owners and lessees of 2003-2005 model vehicles.

Lexus achieved high ratings from repair customers in the areas of service initiation and service quality.

The study measures the satisfaction of vehicle owners who visit the dealership service department for maintenance or repair work during the first three years of ownership, when the vehicle will typically still be under warranty.

J.D. Power says customer satisfaction with dealership service affects the bottom line for dealers.

Customers who are satisfied with service they received from their dealership service departments are more likely to return for service, buy the same make and recommend the make to others, the research firm says.

J.D. Power says a CSI score gain of 10 points for satisfaction with the service adviser or in-dealership experience can add between $40 to more than $300 per customer annually, averaged over a one-to three-year customer base.