Yes, you can take a deduction for the donation of your vehicle, but you can't count it twice.
When you report the sale on Form 4797, then you will owe tax on the recaptured depreciation, even if you claimed the standard mileage allowance (which includes a depreciation factor). The recaptured depreciation is calculated using the number of miles you claimed for business for each year times the amount from the table in the screenshot, below.
You can either report the sale price as equal to the amount you are claiming for the deduction ($12,000 in your case), then claim the deduction on Schedule A, or you can state the sale price of $0 and not report the deduction, whichever gives you the lowest tax.