The downside to preapproval is that if you wait until you’ve found a car to begin shopping for a loan, someone else might get to the car first. If you plan to go this route, make sure to start this process a bit before you’re ready to purchase.
Consider getting pre-qualified early on in the process as you set your budget, too. This preliminary step doesn’t affect your credit score, and it should make it easier to find the right loan once you’re ready to buy.