It's possible to get some flexibility
The work hours are out of control because management does not know how to set proper work schedules. Sure there is an opening time and a closing time, but double bookings are rampant leaving customers upset when services are not performed within promised scheduled times.
Lube techs are double booked to work on a particular day and then on another day no one is booked to work to serve the customers. Customers get upset and the Shuttle Driver gets to hear all the stories about past poor performances.
Hours for technicians are set