Not all states allow a grace period in which to obtain auto insurance on a new car. Many require you to have insurance before driving off the dealer's lot with your new motor vehicle. The Pennsylvania Driver and Vehicle Services' fact sheet on buying and selling cars states "it is the applicant’s responsibility to contact his insurance agent or broker within 30 days of purchase to extend coverage to the newly purchased vehicle."

You can contact the Pennsylvania Department of Transportation's Financial Responsibility Section to find out more about what PA law says about a grace period for acquiring car insurance on a new vehicle. You may want to see if the 30 days they mentioned is for insurance being extending because of replacing a vehicle on the policy or to start up a new policy for the new car.

There are some insurance companies that will automatically cover a new car for a certain amount of time (usually a few days to 30 days) but typically this is only if you are replacing a different car on the policy with this new car. If this is the case your new car would have the same coverages on the car it is replacing on the policy until you call and actually add the vehicle and the coverages you want on it.

If you already have car insurance on other vehicles, then contact your insurance agent to see if your current policy will cover a new car for a certain period of time. If you do not have a car insurance policy then it would be advisable to shop around for car insurance rates and start up a policy on the vehicle so that you are covered properly as soon as you leave the car dealership's lot.