Hi @carolcurrier101 let me offer some insight. When a company car is used for personal use that use becomes non deductible for business purposes. If you use a flat mileage deduction rather than actual expenses it becomes relatively easy to calculate percentage of miles driven personal vs business but even that calculation can be used against actual vehicle expense to reduce what the business can deduct.
Another consideration is that providing a car to an employee for their personal use may be a taxable fringe benefit and would have to be included in their gross pay.
As complicated as it can be I echo the suggestion you discuss this with an accountant
