By plugs (they pretty much go well over 100k these days), and occasionally by coils, if coils it’s very easy to check by swapping packs and seeing if the code moves. Rarely will you need to swap all of them.

I’ve had very bad experiences with jiffy lube decades ago, they are barely competent enough to change oil, they broke the air box of my car too and even suggested I change my transmission because the oil was dirty, I had the transmission replaced a month ago and wanted it in writing it was dirty (I knew it wasn’t) so I could press for warranty work at the transmission shop.

The manager basically caved at that point and I’ve never gone back. I do my own changes now, but avoid quick lube shops if I can at all costs.