The quality of new vehicles has improved again with the 2018 model year, and Genesis, Kia, and Hyundai rank at the top of the J.D. Power 2018 U.S. Initial Quality Study, which measures problems in the first 90 days of ownership.

New-vehicle quality has improved for four consecutive years, according to the firm, which ranks brands by problems per 100 vehicles (PP100). Quality improved in six of the eight categories measured, and 21 of the 31 brands improved their quality from 2017. The industry average of 93 PP100 improved by four.

The Porsche 911 had the lowest number of problems of any individual vehicle (48 PP100). Domestic automakers Fiat Chrysler Automobiles, Ford Motor Co., and General Motors improved at a rate that outpaced other automakers by lowering their scores by seven, five, and four per 100 vehicles respectively.

Hyundai's Genesis ranks highest as an individual brand with 68 PP100 followed by Kia (72) and Hyundai (74). The top five includes Porsche (79) and Ford (81). Mazda is the most improved brand with a 25 PP100 decline.

Ford also earned the most model-level awards with vehicles that topped their segment such as the Expedition, Mustang, Super Duty trucks, Lincoln Continental, and Lincoln MKC.

Related: Vehicle Dependability Improves 9%: J.D. Power