NEW YORK — Lexus once again stands alone atop a closely watched ranking of vehicle dependability after Buick slipped from the No. 1 spot it shared with the Japanese luxury brand last year, J.D. Power and Associates said.

It's the 14th straight year Toyota Motor Corp.'s high-end brand has held the top position in the annual study, which measures problems experienced by the original owners of vehicles after three years. Lexus had 120 problems per 100 vehicles, down from 145 last year.

"That's a pretty good track record," said Dave Sargent, J.D. Power's vice president of automotive research. "They benefited to some degree ... where a couple of their very important models in their second year on the market — the ES and the RX, which together account for over two-thirds of Lexus sales — both improved significantly."

Ford Motor Co.'s Mercury brand ranked second, followed by General Motors Corp.'s Cadillac. Toyota was fourth, and Honda Motor Co.'s Acura luxury brand was fifth. Land Rover, which Ford sold this year to India's Tata Motors Ltd., was the worst-performing brand, with 344 problems.

The industry average improved to 206 problems per 100 vehicles, from 216 a year ago.

Buick, owned by GM, fell to sixth place in this year's study with 163 problems, although its now-discontinued Buick Century was the top-ranked vehicle in the midsize car segment.

Buick spokeswoman Debbie Frakes said J.D. Power's study is only one of several that the company focuses on. "Obviously we're disappointed not to have been at the top, but as a brand we consistently rank high in many, many quality studies," she said.

The No. 1 problem cited in the study, based on responses from more than 52,000 original owners of 2005 model-year vehicles, was wind noise, followed by noisy brakes, pulling to the left or right, dashboard issues and window fogging. The study weighs all problems equally.

Vehicle dependability has been steadily improving across the industry overall, Sargent said. Since the 2005 study, the industry average has improved from 237 problems per 100 vehicles to 206 this year.

The types of problems reported have trended toward "soft" problems, like funny noises or aesthetic wear, in place of "hard" problems such as major technical defects, Sargent said.

Besides the Buick Century, one other GM vehicle was ranked the best in its segment: The Chevrolet Monte Carlo took the honor amid midsize sporty cars. Ford led three categories with the Crown Victoria large car, the Ford Ranger midsize pickup and the Mercury Monterey minivan.

Chrysler was the only Detroit automaker with no brands ranked better than average. Chrysler spokeswoman Mary Beth Halprin said its namesake and Dodge brands improved their ranking from the 2007 study and have improved by 24 percent over the past five years.