I tried being open Saturdays 8:30 - 2:00 for 8 months with advertising through emails and Facebook and all we really got were DIY'ers wanting us to bail them out at 1:59, a few oil changes, and lots of State Inspections (which the State of Maine mandates cannot be over $ 12.5 [i added on a Saturday $12.50 Saturday convenience fee which people gladly paid]. The only tech willing to work Saturday was an apprentice.
Occasionally we got a decent paying job. I thought with so many Boston area commuters, we would be busy but no. Once summer came, it died because people want to play and not be without their car (even though we have a fleet of loaners) and with summers being short and winters long, I figured I would rather play on the weekends like my customers. Having started in 1976, being open on Saturdays is not going to improve the remaining years I have left.