The OEM cap's are aluminum and so are the threaded part of the valve stem. I had lost one on my car and had just put a chrome one on that I had laying around. When I made a trip to the tire shop to have my 285"s put on the rear the tire guy noticed it and said I should not be running it on there. When I asked him why, he told me that the aluminum and the chromed cap that I had put on could have a reaction to each other and cause corrosion. He said the main problem was that if they did get corroded together that when you tried to unscrew the cap that it could break loose the TMP valve stem seal, then you would have to break down the tire on the wheel to retighten it. I have worked in many different fields in my life and I do have some knowledge of metals and what he said is true, so if you want to run something other than the OEM aluminum caps (except plastic), I would use a little antisieze.