Editors' pick: Originally published Sept. 1.

Car loans are piling up at a frightening pace, but the best rates are still elusive.

The Federal Reserve Bank of New York notes that U.S. auto loan debt stood at $1.1 trillion in June. That's $97 billion more than it was a year ago and is the second-fastest-growing portion of consumer debt behind only the $246 billion increase in mortgage debt from 2015 that brought the nation's mortgage tab to $8.36 trillion.

Auto loan debt is now perilously close to the total amount of U.S. student loan debt ($1.26 trillion) and is nearly $400 billion more than the nation's $726 billion credit card debt. The good news is that the 3.5% of auto loans that are past due are minuscule compared to the 7.2% of credit card debt and 11.1% of student loan debt that's similarly in arrears.

The bad news? It's still more than the 1.8% of mortgages that are behind on their payments and is up from 3.2% in 2014 and just 2.2% in pre-recession 2006. It also doesn't help that 22% of all car loans fall into the "subprime" category of borrowers with credit scores of 620 or less.

"Growth rates continue at unsustainable levels," said Nick Clements, former banker turned consumer advocate and founder of personal finance advice site MagnifyMoney. "Too much risk is being taken, and defaults will be coming."

Even new auto loans at credit unions a have jumped 15.7% within the last year, accounting for 18.4% of total loan growth, increasing $20.7 billion year-over-year and adding 572,550 new auto loans the national total, according to credit union analysts Callahan & Associates. Used car loans, meanwhile, rose 13.4% since August of last year, account for 25.8% of all loan growth during that span and have an average balance of $11,941.

Unfortunately, even at credit unions, auto loans don't always tend to be a great investment. The folks at CreditCards.com note that of all loans that required a co-signer during the last year, 51% were auto loans. Unfortunately, 38% of co-signers were stuck with all or part of the bill because the borrower couldn't pay. That resulted in a drop in credit score for 28% of co-signers, while 26% say it damaged their relationship with the person they cosigned for.

"With a 38% chance of losing money and a 26% chance of damaging a relationship, co-signing doesn't sound like a very good bet," says Matt Schulz, CreditCards.com's senior industry analyst. "If you absolutely have to co-sign, then at least be aware there's a sizable chance you'll lose some money and/or get your feelings hurt."

However, a lot of the ugliness above can be avoided if you have excellent credit and a lender willing to provide a low rate as a result. With the help of Rate Watch, a Fort Atkinson, Wis.-based premier banking data and analytics service owned by TheStreet, Inc., we found the ten best auto loan rates in the country. If you manage to qualify, use them wisely:

This article is commentary by an independent contributor. At the time of publication, the author held no positions in the stocks mentioned.