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Most-improved player Mercedes-Benz again leads an annual ranking that measures the sales effectiveness of different auto brands’ dealers.

This is the third year in a row Mercedes has topped Pied Piper Management’s independent Prospect Satisfaction Index.

The consultancy sent 3,524 mystery shoppers into dealerships. The covert operatives recorded how sales personnel did on matters ranging from product knowledge to whether they gave compelling reasons to buy, to whether they provided vehicle walk-arounds.

Mercedes dealers collectively merited the highest index rating of 108. Jaguar and Lexus dealers tied for second with an index of 107. Acura and Infiniti placed third, each scoring 106.

At the bottom of the list were Mitsubishi (91), Suzuki (98) and Smart (100). The low scores largely reflect those brands’ anemic sales in recent years, says Pied Piper CEO Fran O’Hagan.

Mercedes earned only a so-so score on the firm’s first index of 2007, he says. “Mercedes was at the low end of the luxury brands.”

The German auto maker’s American dealer body went to the top of the ranking for “one main reason,” O’Hagan says. “Ernst Lieb showed up in the U.S.”

As president and CEO of Mercedes-Benz USA, Lieb set up a process guiding how Mercedes dealers treat customers. The auto maker now measures performance and rewards dealers who do well.

Did the power of Lieb’s personality or the strength of the system produce the desired results among Mercedes 350 U.S. dealers?

“Both,” O’Hagan tells Ward’s. “A lot of dealer-improvement programs are out there, and they haven’t been as successful. Lieb will tell you money motivates. And Mercedes dealers are very profitable. You will see differences between a Suzuki dealer delivering five units a month and a Mercedes dealer delivering 55.”

If dealers struggle to make money, “they will not be able to offer the service our customers deserve and pay for,” Lieb recently told journalists in Detroit. “Dealers are such a huge part of what we do.”

Among the brand’s stand-out dealerships is Mercedes-Benz of San Francisco, near the heart of that city.

“We’re not on an auto row, we’re downtown, so as a ‘destination’ dealership we strive to provide exceptional service to our clients,” Ash Zaki, the store’s general manager, tells Ward’s.

It apparently is working. The dealership typically delivers 90 new and 90 used units a month. “We’re doing a lot more used cars than before,” he says.

Overall auto-industry performance on the Pied Piper prospect satisfaction index has declined from 2010 to 2011.

Compared with last year, sales people were less likely to:

• Mention maintenance programs and costs.
• Address specific features and benefits relevant to the shopper.
• Discuss features different from the competition.