If you buy another car, your policy might automatically cover it with certain limitations. Read your policy to know whether it automatically covers an additional or replacement car.
In general, an additional car usually has the same coverage as the car on your policy with the broadest coverage. For example, if you have two cars (one with liability coverage only and one with liability, collision, and comprehensive coverage) and you buy a third car, the third car will automatically have liability, collision, and comprehensive coverage.
A replacement car usually has the same coverage as the car it replaced. For example, if you trade in an older car that only had liability coverage; the new car will automatically have only liability coverage.
Be sure to tell your insurance company as soon as possible that you have added or replaced a car and which coverage you want. You could lose coverage on an additional or replacement car if you wait longer than the number of days specified in your policy to notify your insurance company.