If you claim a total deduction of $5,000 or less for all contributed property, you need only complete Section A of Form 8283
If you claim a deduction of more than $5,000 for an item or a group of similar items, you generally need to complete Section B of Form 8283
(PDF) which requires, in most cases, an appraisal by a qualified appraiser.
You will need to obtain and keep evidence of your car donation and be able to substantiate the fair market value of the car.
If you are claiming a deduction of $250 or more for the car donation, you will also need a written acknowledgement prepared by the charity at the time of donation, that includes a description of the car and a statement of whether the charity provided any goods or services in return for the car and, if so, a description and estimate of the fair market value of the goods or services.