It is generally recommended that all licensed drivers in a household be listed on the car insurance policy, including adult children who may be using the car. However, it is possible that the insurance company may not require you to be added to your dad's policy if you are over the age of 25 and have a clean driving record. It is best to check with your dad's insurance company to determine their specific requirements. If you are added to the policy, it may result in an increase in the premium, but this will depend on a variety of factors, including your age, driving record, and the type of car you will be driving.