Too many people have the wrong idea that because they are covered to drive the car that is listed on the policy that coverage will extend to any car they drive. This misinformation could really get you in trouble.
Suppose you are offered a car to drive that doesn't have insurance but the tags are good. You are borrowing it and it doesn't have insurance. You say to the owner, "Ah, it's okay, I got full coverage insurance on my car, I'll be covered." You grab the ID card out of your own car thinking it's going to protect you and provide proof to the cops.
Wrong! You might be covered for your own medical bills if you are in an accident as your personal injury protection (PIP) follows you around as a pedestrian or passenger in another vehicle, but your liability insurance does not. The least that could happen is that you get pulled over and the borrowed car gets impounded. You'd then walk away from the scene with a ticket in your hand for driving with no insurance and potentially an SR-22 requirement from the Oregon DMV for the next three years. The worst that could happen is that you are involved in an accident and find out the hard way that the accident isn't covered. That gets you not only an SR-22 requirement but maybe a one year suspension on your drivers license.
Insurance follows the car in Oregon means the owner of every car registered at the Oregon DMV must be insured by its owner, running or not. If the plates and tags are good, the automobile must be insured. Your own insurance on your own car back home does not extend to cover cars that belong to other drivers. If you borrow another person's car you will be covered under the policy that covers that car, not your own.
Another scenario is your friend has just bought a car and you place it on your policy. Your friend doesn't live with you nor is he listed on your policy as a driver. Technically the car is not yours. It belongs to your friend. He is the one responsible for insuring it. Not you. I know, you are just trying to help him out. But you have no idea the risk and he are taking by attempting to insure a car that doesn't belong to you on your policy while he drives off not listed on the policy as a driver. Never insure a car that doesn't belong to you or to one of the drivers authorized and listed on your policy. You might find out the hard way after a crash that the company will do everything it can to deny the claim.
Follow this simple rule of thumb. If YOU own the car YOU must insure it. Always ask when you get into someone else's car, as a driver or a passenger if they have insurance. Don't just assume. Make sure you know where the proof of insurance is located in the vehicle as well as the registration. If you get into an accident or pulled over by the police, you will need that documentation. Your policy information on a different car won't help you.