This post comes from Gerri Detweiler at partner site Credit.com.

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A year and a half ago, I bought my first brand-new car. Until then, I'd always bought used. But thanks to the recession, people were holding on to their cars longer, and prices for used cars in good shape with low mileage had risen. As a result, buying new made more sense.

Image: Couple shopping for car (© Don Mason-Blend Images-Corbis)
While I find auto shopping completely stressful, I am luckily married to someone who loves the hunt and doesn't mind spending hours researching vehicles. But I wasn't about to let him loose without clear parameters.

So before I headed out to start my car-buying experience, I had a slew of options for my first step:

Although I did all of those things, the very first thing I did was check my credit scores to make sure there were no problems with my credit. I needed to finance my new car, and I knew that getting a good interest rate would be just as important as negotiating a good deal on the vehicle I chose.

Whether you're buying a new or used car, as long as you plan to finance it you'll want to make sure you don't overlook this crucial step in the car-buying process. And I am not just saying that as a credit expert. Car-buying expert Phil Reed, who has bought at least one car every two months for most of the 12-plus years he has worked at Edmunds.com, warned in a recent interview that prospective buyers who don't take this extra step may pay far more for a car loan than they need to.

So what happens is they go directly to the dealership without checking their credit scores -- which is not a good thing to do -- and their attitude is "get me done." In fact, that's sort of a slogan that some car salespeople use; this (customer's attitude) was just "get me done." And that means that the borrower almost feels that the dealer is doing them a favor by giving them a loan. If they had taken time to check their credit, they might have found that they were in a stronger position. However, what happens is the dealership will go ahead and possibly offer them a loan that's 2% to 5% higher than it could be .... But even two percentage points on a $25,000 loan is going to mean nearly $1,000 to $2,000 more over the term of the loan.

The Consumer Financial Protection Bureau is also concerned that some buyers are steered into more expensive auto loans. It recently announced that it will be clamping down on potentially "unlawful discriminatory pricing" in auto loans. Its focus is "dealer markups" -- where dealers charge more than the rate the lender is offering in order to make more money -- which the bureau says can add significantly to the cost of a loan.

When it comes to car loans, we're talking big bucks: The CFPB says that there was about $783 billion in outstanding auto loan debt in 2012 and that auto loans are the third largest source of debt after mortgages and student loans.

Why does the dealer's score look different?

If you do check your credit scores before you start shopping for auto financing, you will probably find that the number the dealer or financial institution sees is different from the number you see. That doesn't mean your free credit score is wrong. It's different because there are many credit scores out there, and the credit scores used by the auto industry are usually customized to help them predict how likely the borrower is to pay that type of loan on time.

So when you do check your credit scores, be sure to focus on where you fall in comparison with other consumers, what areas of your credit are strong -- and what might need some work. For example, if you get your free Credit Report Card from Credit.com and earn an "A" in all the factors that make up your credit score, you know you should likely be getting a great rate on your auto loan. But even if some areas rate a "B" or "C," you may still be able to snag a good deal.

Once you know where your credit stands, you can shop for an auto loan before you set foot in a dealership. When you find the car or truck you want to buy, you can take the financing you have already lined up, or let the dealer make you a better offer. Either way you can enjoy your new vehicle knowing that, at least as far as financing goes, you got the best deal possible.

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