Lexus makes the best-quality cars in the US, and automakers overall are much better at eliminating problems that land vehicles in the repair shop, according to a new JD Power survey of car owners.Toyota's luxury brand had the fewest problems per 100 vehicles in a survey of 2012 models by research firm JD Power and Associates in the US. The brand was followed by two other luxury carmakers, Jaguar and Porsche, which tied for second place. Cadillac and Honda rounded out the top five.Cars and trucks sold in the US had the highest quality since JD Power started doing the study in 1987. Still, quality was hurt by widespread glitches in technology such as touch-screen controls and voice-recognition software, said David Sargent, the firm's automotive vice president.MONKEY SEE, MONKEY DOSargent said automakers have learned quality manufacturing techniques from top competitors, and they're using higher quality materials than in the past. Quality has improved so much during the past decade that the difference between the best and worst brands is less than one problem per vehicle, according to the study.Sargent said: "Everybody in the industry knows that if they don't keep improving, they're going to fall behind."In the US survey, JD Power asked 74 000 people who bought or leased 2012 models about how reliable their vehicles were and whether they had problems with knobs, switches, electronics and other items in the first 90 days of ownership.In the JD Power survey, the entire industry cut the number of problems per 100 vehicles by five to a score of 102.Here are some highlights from the study:WINNERS: Lexus owners reported only 73 problems per 100 vehicles. Lexus wins consistently because quality and customer service have guided the brand since its first car went on sale in 1989, Sargent said. Cadillac was Detroit's top entry at fourth, and Honda was the highest-ranking mainstream brand at fifth.LOSERS: Italy's Fiat tied for last in quality with Mercedes' Smart brand. Both had 151 problems per 100 vehicles.BEST MODELS: Ford and Lexus had the top cars or trucks in three categories. Infiniti, Nissan and Toyota each won two categories.TECHNOLOGY WOES: Sargent said the poor quality scores for new technology came because people had trouble adjusting to the devices, and because some of them don't operate right. Electronics are making their way from luxury to mainstream brands where they are new to people. "There are a lot of problems where the system just doesn't work as designed," Sargent said.MOST IMPROVED: Jaguar, which went from 21st place last year to second this year, and Nissan, which improved 11 spots to tie for 12th. Jaguar was weighed down last year by problems with the XJ model, which was new for 2011. Fixing those problems vaulted the brand, which has only three models, toward the top, Sargent said. Nissan improved by hard work across all of its models, he said.GOING BACKWARD: Troubles with touch screens and automatic transmissions continued to hurt Ford, which finished 27th out of 34 brands in the survey. Ford was a star in 2010 at fifth place, but tumbled when it introduced its complicated MyFordTouch screens. Buyers also were annoyed with constant shifting by transmissions in small cars.