If you use the standard mileage rate then all you need to keep is the mileage information. If you convert the auto to personal use then there is no recapture.
As far as using it for business then you are required to deduct the auto expense and keep the records since you must deduct all valid business expenses. Of course if you are not in the Earned Income Credit range then the IRS will effectively ignore that rule and let you pay more in taxes if you like.
