General Motors has confirmed that Cadillac earned the highest ranking among 12 different luxury automakers, and Buick ranks the highest among 19 mass-market companies in the J.D. Power 2014 U.S. Customer Service Index study.

Other automakers to place in the top five for luxury vehicles includes: Audi, Lexus, Infiniti, and Lincoln.

Lexus had finished first in the luxury category the last five years.

Volkswagen, GMC, Mini and Chevrolet finished behind Buick in the mass-market rankings, according to the survey.

Winners are determined based on customer satisfaction with dealership service departments.

"What makes this survey so valuable is that it is an objective measure of service satisfaction," said David Mingle, GM executive director of customer experience, in a statement, according to the automaker. "The results of this benchmark study confirm our commitment to provide our customers with the best overall experience in the entire industry."

The study measures service satisfaction among owners and lessees of one- to five-year-old vehicles sold in the U.S.

Five service areas are focused on, including: service initiation, service advisor, service quality, vehicle pick-up, and service facility.

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