The staff recommended a toll package for $15 a day, but Chicago doesn't have many toll highways. I didn't buy it and just set the GPS to avoid toll roads. I drove for three days and visited most of the popular attractions without encountering any toll fees. Near O'Hare Airport, highways are often congested. If you didn’t purchase the full tank package, it’s better to fill up the tank elsewhere before getting on the highway; otherwise, you'll face half-hour traffic jams entering or exiting the highway. Plan your time accordingly.