The deductibility of a vehicle is determined by who owns the vehicle, the business or an individual. If the business owns the vehicle, you would not track mileage as all expenses of the vehicle are deductible, including depreciation.
If the vehicle is owned by the individual and used for business purposes, then the individual would submit an expense report to the business which will indicate the beginning odometer reading, the ending odometer reading, the date, the business purpose of the trip, and the total mileage. The business would reimburse the individual for the business mileage only. Also, the vehicle would be depreciated based on the percentage used for business.
Here is an IRS publication with details the allowable deductions for vehicles owned or leased which are used for business: https://www.irs.gov/taxtopics/tc510
