Do they do oil changes without appointments on Saturdays?

Yes, most Saturdays first come first serve-9am-about 3pm to get started, both locations

I believe there a Quick Lane Oil Change and I think that if you'd wait in the waiting room they'll change your oil for you if you're only speaking of engine oil but because Harley-Davidson some models have three oils I don't know if they can do that but a single oil change I never had a problem on a Saturday hope this helps you