The race to increase vehicle fuel economy is taking a toll on quality.
American owners of three-year-old vehicles are reporting more problems than they did a year ago, according to JD Power and Associates' annual survey of vehicle dependability.
It's the first time since 1998 that the average number of problems per vehicle has increased.
JD Power, a California-based ratings and consulting company, said engine issues accounted for most of the increase in problems reported by the original owners of cars and trucks from the 2011 model year.
Owners reported an average of 133 problems for every 100 vehicles, up from 126 problems a year ago. Only problems within the prior 12 months are counted.
Auto makers are rapidly implementing new engine technology to save fuel, including direct fuel injection and turbocharging, stop-start systems that automatically shut down cars at traffic lights and transmissions with higher gears.
But those more complex systems can cause problems.
JD Power's vice president of global automotive, David Sargent, said the company noted an increase in complaints about engine hesitation, rough transmission shifts and lack of power.
"While striving to reduce fuel consumption, auto makers must be careful not to compromise quality," Sargent said in a statement.
Lexus, Mercedes-Benz and Cadillac had the vehicles with the fewest reported problems.
Lexus had just 68 problems for 100 vehicles, the only brand with fewer than 100 problems.
General Motors had the most winners in each segment, with eight, including the highest-ranked compact car, the Chevrolet Volt, and the highest-ranked utility, the GMC Sierra.
Toyota was second with seven segment winners, including the Toyota Camry minivan and Lexus ES luxury compact car.
Mini, Dodge and Land Rover had the most reported problems.
Mini, the worst performer, had 185 problems per 100 vehicles.
The survey questioned 41,000 owners of 2011 model-year vehicles between October and December of last year.
