A customer came in on Saturday and brought this filter in. This is the engine mounted fuel filter on a Ford 6.0L Powerstroke, there is one mounted on the frame, as the picture of new filters shows. He said he just wanted the o-ring for the housing since it was leaking and he put RTV around it a few years ago and that started to leak. Now the book says to change them both every 15K miles, you have to buy them as a set. Most owners do them a lot more frequently to try and extend injector life. I told the customer that we don't stock the o-ring by itself, I could order it but it wouldn't be in until Tuesday. However we stock the filter set and I am guessing by him saying he RTV'd the cap a few years ago and since the frame mounted one will get that discolored if you extend the interval, he should do them. He balked and said it was too expensive but I ended up selling the filter set to him at wholesale cost. He then got upset that he had to get both. After he left I realized what a terrible thing I had done. That 2004 F-250 probably had the factory filters still in it and was probably one of the only 2004 6.0s to never have any work done beyond oil changes every Presidential Inauguration. I kept it until Monday to show our diesel tech who about fainted seeing it.