I worked at VIOC over 15 years ago back when they had a fast track managerial program. Valvoline as a company was never a problem to work for. The problems came from the district manager assigned to the group of stores. If they did not embrace the program life was made very tough as you got no support or help at all. I ending up leaving and group of other managers also left soon after before they caught on and replaced the DM. Things have completely changed since then from talking to employees and I believe it would be a good part time job if you enjoy the type of work.
FYI weekends and nights were the busy times. Weekdays during the day were the slowest back then and I doubt that has changed.