DETROIT — The quality of new cars improved across the industry this year, with Porsche, Honda, Toyota, General Motors and Ford among the automakers leading the pack, the marketing and consulting company J.D. Power and Associates said yesterday.

Porsche was the top brand in J.D. Power's annual ranking of initial vehicle quality, which measures both mechanical and design problems in the first 90 days of ownership. Others in the top five were Nissan Motor Co.'s Infiniti, Mercedes-Benz, and Toyota Motor Corp.'s Lexus and Toyota brands.

Honda was the only brand with three winners — the Fit subcompact, Civic small car and CR-V crossover. Toyota, General Motors Corp. and Ford Motor Co. had three winners each across all their brands. Overall, 26 of the 36 nameplates in the rankings improved from last year.

Chrysler LLC's Jeep was the worst performing brand, with 167 problems per 100 vehicles. Other brands in the bottom five were BMW AG's MINI, Land Rover, GM's Saturn, and Suzuki.

David Sargent, vice president of automotive research at J.D. Power, said the most improved vehicle this year was the Volkswagen Passat. He also cited the Chevrolet Malibu and Infiniti EX-Series, saying both vehicles had strong launches with relatively few problems.

J.D. Power says overall quality improved to an average of 118 problems per 100 vehicles from 125 problems last year. Vehicle quality has improved over the last decade; there were 176 problems per 100 vehicles in 1998.

The rankings were based on questionnaires from 81,500 people who bought or leased new 2008 vehicles between November and January.