DETROIT – Porsche holds its overall top ranking for a third consecutive year in the J.D. Power and Associates 2008 Initial Quality Study, while 12 of 16 General Motors Corp.’s Chevrolet models improve over last year.

The annual study measures customer satisfaction during the first 90 days of vehicle ownership. The 2008 IQS results were calculated from the responses of more than 81,500 buyers and lessees of new ’08 model vehicles gathered between February and April.

Porsche models averaged 87 problems per 100 vehicles this year, improving from 91 in the 2007 IQS. The industry average for 2008 is 118.

Audi posted the biggest gain in the 2008 survey, climbing to 8th place in overall nameplate ranking, from 26th in 2007. Audi models averaged 113 problems per 100 vehicles surveyed, compared with year-ago’s 136.

Four GM brands ranked above the industry average this year, including Cadillac, Chevrolet, Pontiac and Buick, all of which leaped ahead of prior-year’s IQS.

Cadillac and Chevy tied with Audi for 8th place in overall nameplate rankings. Cadillac averaged 135 problems per 100 vehicles, while Chevy scored 129 in the 2007 IQS.

Pontiac tied with the Hyundai brand for 9th place, each with 114 problems per 100 vehicles. Both showed improvement over last year’s results. Buick scored 118 problems per 100 vehicles, up from year-ago’s 127.

GM also earned three top model-segment awards. The Chevy Malibu placed first in the midsize-car category, ahead of the Ford Fusion and Mitsubishi Galant. The Pontiac Grand Prix sedan ranked No.1 in the large-car category, outpacing the Mercury Sable and Grand Marquis.

The heavy-duty Chevy Silverado took the top spot in the large pickup segment, besting the Toyota Tundra and Chevy Avalanche.

Ford Motor Co.’s namesake brand, which scored well last year, saw improved IQS results, with 112 problems per 100 vehicles, compared with 120 in 2007.

Other significant improvements include Nissan North America Inc.’s Infiniti brand, which places second to Porsche in this year’s IQS, with 98 problems per 100 vehicles, moving from ninth place last year and 117 problems per 100 vehicles.

The Toyota brand pulled ahead of 2007’s 112 problems per 100 vehicles to 104 this year, good for a fourth-place tie with Mercedes.

Mercedes improved from last year’s 111 problems per 100 vehicles to this year’s 104, while Toyota Motor Corp.’s Lexus slipped to third place from second last year, with 99 problems per 100 vehicles compared with 94 in 2007.

Jaguar in its last year under Ford ownership, paced last year’s score of 112 problems per 100 vehicles. Land Rover pulling ahead of its last-place spot in 2007, albeit it third to last, with an improvement of 161 problems per 100 vehicles compared with year-ago’s 170.

Bringing up the rear in this year’s IQS was Chrysler LLC’s Jeep brand, with 167 problems per 100 vehicles vs. 161 in 2007. The Chrysler and Dodge brands showed improvement but still fell below the industry standard.

“Due to some strong, new-vehicle launches, in addition to continued reduction in the level of defects and malfunctions, overall quality improves by 6% in 2008, compared with 2007,” Dave Sargent, vice president-automotive research at J.D. Power, says in a statement. The nameplate industry average in 2007 was 125 problems per vehicles.

While 86% of the overall improvement can be attributed to advances in curing defects and malfunctions, J.D. Power found consumers frustrated with in-vehicle technology.

“Minimizing design problems remains a major challenge for the industry,” Sargent says. “Issues with difficult-to-use audio and entertainment controls and voice-command recognition failure are among the top 10 problems most frequently reported by customers.”

On the positive side, Sargent says the Chevy Malibu and Infiniti EX were by far the best-performing vehicles. He calls the EX’s first place award for a premium cross/utility vehicle,” a pretty impressive performance to be No.1 in quality the first year out of the box.”

Sargent also says the Cadillac CTS launch “was pretty competitive in terms of quality.”

J.D. Power also doles out plant awards as part of its IQS.

Mercedes-Benz Sindelfingen, Germany, facility receives this year’s Platinum Award, with 33 defects or malfunctions per 100 vehicles. The plant builds the Mercedes CL-, CLS-, and S-Class, as well as the E-Class sedan and wagon.

The top North or South American plant for 2008 is Toyota’s Baja, CA, facility that makes the Tacoma midsize pickup truck.

Toyota’s newest plant in San Antonio, home of the Tundra fullsize pickup places second, while GM’s Fairfax, KS, plant, site of Chevy Malibu and Saturn Aura production, is third.

In Asia, Toyota’s Prius Hybrid plant in Fujimatsu, Japan, garners the top spot, with Porsche AG’s 911 plant in Stuttgart named the top European plant.

cschweinsberg@wardsauto.com