I get a lot of work done at our local Kwik-Kar lube center and I will have to say that they appear to be very honest. They only tried to sell me a new air filter once. I knew it needed replacing and I even had purchased a new K&N filter, but had not installed it yet. After I installed the K&N they never tried to sell me a new air filter, or any other service that I knew I never needed.
I am allowed to go into the work bays, and was present and watching both transmission flushes they did on both of my Sport Tracs. I talked with the service manager when he was doing my transmission flush and he appears to be knowledgable and competent and I have never seen anywone push unneeded products or services on anyone. My only gripe is that when I first went to get tranny flush they tried to say that they could not get to it for several hours. I later found out that the service manager is the only guy allowed to do the tranny flushes, and he was not there when I showed up the first time.
The shop is owned by a woman who lives in our community and if they were ripping people off, the word would be out fairly quickly. Even the local police take their cars there for service.
PS: I am not vouching for all Kwik-Kar Lube shops, I just feel that the this one in my home town does honest dependable work at a very reasonable price. I'm sure there are Jiffy Lubes, and other lube centers that do honest work, but there are many like Todd said that are pushed to sell more products and services regardless whether the customer really needs them or not.
...Rich