Is the excess amount from the insurance, after repairing the borrowed car, the right of the borrower or the owner?

It is known that insurance is for the car and its owner, not for the driver. So, if the driver, acting as an agent for the car owner, agrees with the insurance company on a sum for damages, and then finds someone who can repair the car for less, the remaining amount belongs to the car owner (the principal), unless the owner gives it to him.