I work for a Jiffy Lube in NY, I was reading through some of the complaints you have posted, and not to be rude or anything, but some things just take a little a thought. For example, the broken windshield, the windshield was used, why should Jiffy Lube buy a new one, as long as it is fixed, and at minimum, holds the same value that the original was in, it should be considered even. The poor installation job, is not Jiffy Lubes fault, we do not install windows, talk to the person that does.
Also I read that Jiffy Lube has a big team of lawyers to lie and get out of being held responsible, well that's not totally the case. It only makes sense for a big franchise to have good lawyers. Working at Jiffy Lube I have seen many customers come in with false accusations that we "broke" their car. In most cases the customer either does not know what he/she is talking about, or more commonly is trying to scam Jiffy Lube into getting something for free at Jiffy Lubes expense. I've seen a lot of people place the blame on us for ridiculous things, and its really disturbing to see how people can really be.
So keep in mind, that even tho, yes Jiffy Lube employees are people, and do sometimes make mistakes, we are not trying to deny people who legitimately were wronged their dues, we are trying to protect ourselves from being taken advantage of.
Finally, I read a comment about how Jiffy Lubes are bad, and that people should take their cars to a local mechanic. Impossible, realize how many cars a day a place like Jiffy Lube does, a local shop could never do it. Also even people in small shops make mistakes and have to deal with the same issues Jiffy Lube does, you just don't hear about it, because it is a small business, not a nationally known franchise. Just think about that.
