During the race, work on the car is permitted, but it is usually limited to routine pit stop work (changing tires and refueling) and minor adjustments (wing angles, etc.) Pit stop activity is rigorously rehearsed by the crews and in modern times, routine pits stops are regularly completed in under ten seconds. Other more involved work, such as replacing damaged bodywork (wings, nose cones, etc.), can also be completed quickly by the crews. More lengthy repairs are allowed, and since 1998 teams are permitted to return to the garage area to make repairs. However, there are limitations to the extent of repair work allowed and the practicality of such work. Teams are not allowed to change engines, and since 1933 a rule has been in place where teams are not allowed to add oil. In addition, the officials designate a certain lap after which off-track cars being serviced/repaired are no longer permitted to return to the race.