Deductions & credits

No.  You would not be able to deduct mileage because mileage includes the costs of things like gas, insurance, depreciation, tires, oil changes, etc.  However, you would be able to deduct your actual gas expenses.  To do this, you would go to vehicle expenses in the business expense section and then start entering the information about the vehicle, then when asked if you own the vehicle say "This vehicle isn't mine"  You will then be able to deduct your actual expenses incurred while using the vehicle.