Comprehensive insurance. Interestingly enough, allstate comes out with the highest premium for annual mileage while liberty mutual and usaa compete for the lowest premium for annual mileage. There are a few different kinds of car insurance discounts available in the state of illinois. The cost of car insurance varies depending on your age, marital status, mileage, driving history, and more. All insured drivers share the increasing cost of insurance. Car insurance for drivers with bad credit costs significantly more than it does for those with good credit. This insurance is designed to protect you and your car in the event of a hit-and-run accident or collision involving other drivers who may be uninsured or who may not have enough insurance to cover the costs of damage done to you or your property.