With a 25 year old, car insurance tends to decrease in price dramatically. However, it still may be cheaper to stay on your parents insurance policy. As long as a young adult lives in the same household as their parents, most insurance companies will allow them to stay on the parents policy. Guidelines and regulations vary by insurance company, so check with your insurance agent. It is also a good idea to check pricing on a separate policy without your parents, as prices do drop significantly after 25. When you move out of your parents house, it will be necessary to get your own policy.