Hi,
I have one vehicle that was "maintained" religiously by the former owner at a Jiffy Lube--perhaps "Taken to JL on a regular basis" would be a more accurate description. Took me close to a year to find all the stuff they'd either not done, or screwed up. Since they didn't do the "work" for me, they owed me nothing, but it was aggravating, if not costly, to undo what they'd done previously.
I'm sure most States probably have an automotive consumer protection agency. In CA, ours is called B.A.R. (Bureau of Automotive Repair.) If you have a complaint with a shop, and it's not being resolved, just the suggestion you'll be calling B.A.R. about the issue will usually perk people's ears up. I've no personal experience with the agency, but several people I've known in the auto repair business say getting B.A.R. involved can be about as pleasant as having a root canal in the morning followed by an IRS audit in the afternoon!
Sounds like a lot of Jiffy Lube customers could, and should, make that call... On top of that, here in the land of perpetual litigation, I'm sure there are a number of lawyers out there just rubbing their hands together in glee at the thought of a big class action suit!
Rick C