Because you use the same vehicle for both businesses you have to enter the vehicle under both businesses.
For example, if the total business mileage for the year on the car was 12,000 miles, you would take that mileage and apportion it to the two businesses according to how much you use it for each business--8,000 miles for Business A and 4,000 for Business B.
What if I use the same vehicle for two separate businesses, and for business one i used actual cost? Can I put second business under standard mileage if i use less?
I am not an expert but it seems to me one can own multiple cars, each using a different method. But not all cars have to use same method. It is NOT the business that dictates how a car's expenses are applied but the car itself. Each car has to use a consistent method. You calculate total cost per car. Then apportion a fraction of the total cost to each Schedule C according to the percentage of use by each Schedule C.