If you use your car in your job or business and you use it only for that purpose, you may be able to deduct its entire cost of operation. However, if you use the car for both business and personal purposes, you may deduct only the cost of its business use and you must keep records to support your claim.
Your unreimbursed employee expenses are subject to the 2 percent of adjusted gross income floor on Schedule A.
Publication 17, Your Federal Income Tax - Chapter 26, Car Expenses and Other Employee Business Expenses - Under Transportation Expenses, see Car Expenses for essential guidance
Publication 463, Travel, Entertainment, Gift, and Car Expenses - Detailed guidance