WESTLAKE VILLAGE, Calif. — Owners of three-year-old vehicles (2011 model year) report more problems than did owners of 3-year-old vehicles last year, according to the J.D. Power 2014 U.S. Vehicle Dependability Study (VDS).

Released yesterday, the study examined problems experienced during the past 12 months by original owners of 2011 model-year vehicles. Overall dependability is determined by the number of problems experienced per 100 vehicles (PP100), with a lower score reflecting higher quality.

The study found that overall vehicle dependability averages 133 PP100, a 6% increase in problems from 126 PP100 in 2013. This marks the first time since the 1998 study that the average number of problems has increased.

“Until this year, we have seen a continual improvement in vehicle dependability,” said David Sargent, vice president of global automotive at J.D. Power. “However, some of the changes that automakers implemented for the 2011 model year have led to a noticeable increase in problems reported.”

Engine and transmission problems increase by nearly 6 PP100 year over year, accounting for the majority of the overall 7 PP100 increase in reported problems. The decline in quality is particularly acute for vehicles with 4-cylinder engines, where problem levels increase by nearly 10 PP100. These smaller engines, as well as large diesel engines, tend to be more problematic than five- and six-cylinder engines, for which owners report fewer problems, on average.

“Automakers are continually looking for ways to improve fuel economy, which is a primary purchase motivator for many consumers, particularly those buying smaller vehicles,” Sargent said. “However, while striving to reduce fuel consumption, automakers must be careful not to compromise quality. Increases in such problems as engine hesitation, rough transmission shifts and lack of power indicate that this is a continuing challenge.”

J.D. Power also found that the fewer problems owners experience with their vehicle, the greater their loyalty to the brand. Combined data from previous years’ VDS results and vehicle trade-in data from J.D. Power’s Power Information Network (PIN) show that 56% of owners who reported no problems stayed with the same brand when they purchased their next new vehicle. Brand loyalty slipped to just 42% among owners who reported three or more problems.

Also, a comparison of data from the 2013 Vehicle Dependability Study with data from the subsequent J.D. Power 2014 U.S. Avoider Study shows that consumers are much more likely to avoid vehicles from brands that rank lower in dependability. On average, 23% of consumers avoided brands that ranked in the lowest quartile of the 2013 VDS because of concerns about reliability. In contrast, only 9% of consumers cited that same reason for avoiding brands that ranked in the top quartile.

“By combining our customer research with trade-in data, we see a very strong correlation between dependability and real-world brand loyalty,” Sargent said. “Also, we see that brands with lower dependability are likely to be shut out of a significant piece of the market, as many consumers will not even consider purchasing one of their vehicles because of concerns about its likely reliability.”

Lexus ranks highest in vehicle dependability among all nameplates for a third consecutive year. The gap between Lexus and all other brands is substantial, with Lexus averaging 68 PP100 compared with second-ranked Mercedes-Benz at 104 PP100. Following Mercedes-Benz in the rankings are Cadillac (107), Acura (109) and Buick (112), respectively.

General Motors Co. received eight segment awards — more than any other automaker in 2014 —for the Buick Lucerne, Cadillac DTS (tie), Cadillac Escalade, Chevrolet Camaro, Chevrolet Volt, GMC Sierra HD, GMC Sierra LD, and GMC Yukon. Toyota Motor Corp. garnered seven awards for the Lexus ES, Lexus GS, Lexus LS (tie), Lexus RX, Scion xB, Toyota Camry, and Toyota Sienna. Honda Motor Co. received six model-level awards for the Acura RDX, Honda CR-V, Honda Crosstour, Honda Element, Honda Fit, and Honda Ridgeline. MINI received one model-level award for the MINI Cooper.

The 2014 Vehicle Dependability Study is based on responses from more than 41,000 original owners of 2011 model-year vehicles after three years of ownership. The study was fielded between October and December 2013.