Mercedes-Benz, Infiniti offer best customer service, study says.

While Mercedes-Benz and Infiniti ranked at the top of a customer satisfaction survey, Scion and Mitsubishi dealerships trailed behind other brands at the low end of the spectrum.

Mercedes-Benz, Infiniti, and Lexus dealerships treat car shoppers the best, while at least some Scion and Mitsubishi dealerships have a lot to work on.

These results are some of the top-level findings of the new 2013 Prospect Satisfaction Index (PSI), from the California sales and service consulting firm Pied Piper.

This is the seventh consecutive year that Pied Piper has conducted the PSI studies, and for 2013 it's reset the industry-average score to 100. That leaves an industry low of 88 and 89, for Scion and Mitsubishi, respectively, while Mercedes-Benz stands at the top at 113.

Other top-performing brands included Audi, GMC, Hyundai, Jaguar, and Kia. And according to the firm, 19 of the 33 brands led in at least one PSI sales process. For instance, Infiniti, Land Rover, and Smart were most likely to give a walk-around demo.

Comparing the 2013 results to those of last year, salespeople are now more likely to mention different finance or leasing options, ask about a trade-in, or ask about factors preventing purchase, while they're less likely to offer a brochure, use visual aids, or discuss features that are unique versus the competition.

The company says that, on an individual dealership basis, the PSI survey is closely correlated to sales success. A good point to remember for some of these dealerships that are struggling is that while products might be relatively slow to change, the sales process can change virtually overnight.

The survey was conducted with 5,203 hired “mystery shoppers,” who visited dealerships through the U.S. between July 2012 and June 2013.