If you have your own auto insurance policy for a different car will you be covered if you drive a car not on your policy?

If the vehicle not listed on the policy is a new car that you have recently purchased, you generally have 30 to notify your insurance company of the change. If the vehicle you are driving is just a friends car then, no. Insurance is primary to the vehicle and it is important that the owner of the car have insurance on it and that any drivers of the car be listed as covered on their policy. There are exceptions to everything and these rules will vary by company. It's best to check directly with your insurance company for questions like this.