Americans borrowing record amount to buy cars

A combination of higher prices for new cars and relatively low rates for auto loans means Americans are borrowing a record amount to pay for their new rides.

According to Experian Automotive, which tracks millions of auto loans written each quarter, the average amount borrowed by car buyers last quarter climbed above $27,000 for the first time ever.

"It's not surprising buyers are borrowing more," said Melinda Zabritski, Experian's senior director of automotive credit. "If you look at the most popular segments, they are full-size pickups and SUVs. It's hard to find one of those models new and fully loaded for under $30,000."

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According to Experian, the average auto loan in fourth quarter 2013 was $27,430—an increase of $739 compared with the same period of 2012. The average used car loan was $345 higher, coming in at $17,974.

(Read more: And the February auto sales winners are...)

Those with non-prime credit ratings—or credit scores between 620 and 679—had the highest average auto loan. For these borrowers, the average new car loan rose more than $1,500, to a new high of $29,385.

And as their loans rise, keeping the monthly payment as low as possible has become more of a challenge—even as car buyers stretch their loans over longer periods of time. According to Experian, the average monthly payment for a new car auto loan rose $11 to $471 in the fourth quarter; the average monthly payment for a used car loan edged $4 higher, to $352.

Not surprisingly, those with subprime credit ratings—credit scores between 550 and 619—had the highest average monthly payment, of $499.

"I expect that monthly payment to continue rising and go above $500," Zabritski said. "There's always a tipping point where buyers say, 'I can't pay that much every month.' So far, we haven't seen the flashing lights go off indicating buyers are at a tipping point."

(Read more: Incentives lure car buyers, despite cold)

The payments are rising despite an increasing number of car buyers opting to stretch their loans over six or seven years. According to Experian, a record 20 percent of all new car auto loans in the fourth quarter were more than six years in length.

February auto sales rate: 15.34 million
February auto sales rate: 15.34 million

Overall, the average auto loan is scheduled to last five years and three months—but that could be rising.

J.D. Power said last week that February was on track to have one-third of new car auto loans last at least six years.

Bigger auto loans shouldn't come as a surprise, given the average transaction price—or the amount buyers are paying at dealerships—climbed 1.9 percent to $32,160 in February, according to Kelley Blue Book. It's the second straight month transaction prices came in above $32,000, as car buyers are adding navigation systems, in-car connectivity and infotainment systems to their vehicles.

(Read more: Car buyers commit to longer auto loans)

Within the industry, automakers such as Ford and Volkswagen have average transaction prices higher than $34,000. But for February, the highest average transaction price among the largest mass automakers was General Motors, where the average model sold at dealerships for $35,380.

—By CNBC's Phil LeBeau. Follow him on Twitter @LeBeauCarNews.

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