The study of more than 80,000 repairs performed in 2010 by a network of repair shops that share data with CarMD.com, which tracks repair information, shows that Arizonans pay 18 percent more for repairs.
The study ranks the national average for the labor and parts portions of repair bills and provides an overall percentage.
Arizona was the most expensive state for auto repairs, with overall expenses about 18 percent higher than the national average. Arizona is followed by New Mexico at 14 percent and Colorado at 12 percent.
Car owners in California, with its history of defining automotive culture, pay 20 percent above the national average for labor costs, but combining labor and parts, the combined rate there is 11 percent above the national average. California ranks fourth nationwide overall.
The District of Columbia is the least expensive region. Car owners in and near the Capitol pay 25 percent less than the national average. Missouri, at 17 percent less than the average, Ohio and Wisconsin, both at 16 percent, comprise the least costly states.
Labor costs in the Western states tend to be higher because the repairs relating to problems from dry air and residue from airborne dust tend to be more expensive and take longer to repair, according to CarMD.com.
Also, more temperate temperatures in much of the west and lack of mass-transit in Western states means that motorists living in the region are using their cars more, and that adds up to faster wear and tear.
Repair costs between regions can be substantial based on costs in 2010, the year that the study analyzed. For example, when the check engine light comes on, the typical repair is $421.49 in Arizona, $394.49 in California, and $265.29 in the District of Columbia.
The study analyzed repairs made after check engine lights came on.
A faulty oxygen sensor, which monitors the amount of unburned oxygen in the exhaust, is the most frequent cause for the check engine light to turn on, according to the study. The repair should cost about $260 in parts and labor.
A properly operating oxygen sensor improves fuel economy but a bad sensor can lead to catalytic converter failure, which can cost more than $1,000 to repair. Proper maintenance adds life to the catalytic converter.