The percentage of subprime auto loans saw a big decline in the third quarter despite growing concerns that auto dealers and banks are writing too many loans to borrowers with checkered credit histories, according to new data.

In fact, Experian says the percentage of loans written for those with subprime and deep subprime credit ratings fell to its lowest point since 2012.

"The market turning more prime is an encouraging trend. It indicates that industry professionals are using data and analytics as part of the lending process, and consumers are taking a more active role in managing their credit before buying a car," said Melinda Zabritski, Experian's senior director of automotive finance.

Overall, 25.67 percent of the auto loans written in the third quarter were for borrowers with subprime or deep subprime credit ratings. By comparison, just over 62 percent of the loans written last quarter were for borrowers with prime and super prime credit scores, according to Experian.

The drop in subprime loans comes after months of warnings from critics that banks, auto finance companies and credit unions have issued too many loans to buyers who will be unable to repay them.

In the third quarter, there was a slight decrease in the percentage of loans 30 days overdue and slight increase in those that were 60 days delinquent.

Still, less than 1 percent of all loans were two months overdue, a level below historical averages.

Meanwhile, Experian says the average term for a new vehicle auto loan hit an all-time high of 69 months, thanks in part to a slight increase in the percentage of loans schedule to be repaid over 85 to 94 months.

"We're starting to see some spillover to loans longer than 85 months," said Zabritski.

Overall, the average monthly payment for a new vehicle in the third quarter was $30,329, an increase of $291 from the third quarter of last year.