Cheap Illinois Car Insurance. Introduction Car insurance is a monthly expense that many Illinois residents are required to pay. The amount of car insurance a person needs varies depending on their driving record, age, and the type of car they drive. However, the average Illinois car insurance bill is around $100 per month. Definition of car insurance Car insurance is a mandatory requirement in most states in the United States. The cost of car insurance can vary depending on the state, but on average, it is around $100 a month. Overview of car insurance in Illinois Car insurance in Illinois can be expensive, but it's important to compare rates and find the best policy for your needs. Factors that Affect Car Insurance Rates in Illinois There are a number of factors that affect car insurance rates in Illinois. Age Car insurance rates in Illinois vary depending on the age of the driver and the type of car. Driving Record Vehicle Type Location Average Cost of Car Insurance in Illinois Average Cost of Liability Insurance Shop Around.