I used e-loan just to estimate the best rate I could qualify for, and the dealer worked his tail off to match it (two years ago, 3.9% on a used car, just like Hot Dog).
However, for a new car purchase, you might have to choose between incentives like $2000 cash back OR 1.9% financing. It can be helpful to crunch some numbers beforehand. For example, figure out if taking the 6% loan from the credit union and the $2000 cash back is the better deal or if taking the 1.9% financing is the better deal. There are lots of online calculators, or you can use Excel if you're savvy with writing formulas.
If you get 1.9% (or whatever great rate you can find), you might even want to hang onto your $5K and put it into a savings account earning 5%. Then if your new car gets a flat tire or some other mishap occurs, you're covered. Just be sure you really put it into savings...
Here is a link to a podcast (internet audio series) on buying a car that I found really helpful. It's kind of long, but they share a lot of great tips. You can listen to it on your computer, you don't need an iPod. Good luck!
http://www.mywealthmatterspodcast.co...-your-next-car