Manufacturers often have promotional discounted financing for preferred new car buyers that is better than anything else anywhere. Sometimes as low as 0%. Before letting any dealers check your credit, ask about the availability of such financing offers. Bear in mind, these kinds of offers are typically for new cars and 720+ credit score buyers only, and terms are often limited to 36 or 48 months. If it is available, and you can qualify for it, then you should get it.
Otherwise, credit unions typically having the best interest rates and financing offers. Typical preferred auto rates at credit unions at this time are in the 4% range.
A couple tips:
- If you are looking to buy a new car and know what you want, do not shop by actually going to the dealer lots. Shop by phone and internet first. Actually going to the dealership should be only for doing test drives (and of course, picking up the car when you're ready to buy). I know it can be fun to go to dealerships to get involved in the whole car buying process, but only suckers buy cars that way.
- Dealers do not need to pull your credit to quote you the best rate. So don't let them until you've finally settled on a particular car, dealership, and offer. Call a local dealership and ask a salesperson -- "Hi, I'm interested in buying <blank>, is there any promotional financing available for that model at this time and, if so, what is it?" If the salesperson won't tell you right away, then hang up. This is not like getting a mortgage with a ton of complicating factors that can affect the rate. The promotional rate is either available or it is not. If not, go to the credit union and skip dealer financing altogether.