I have seen a lot of posts on here about the hard assembly of fuel grommets into the tank. A few years ago I found a product called syl glide at auto parts store for just such things. If you have to put a tight fitting rubber thing into a metal hole that is the stuff to use. I think napa uses a different name but it is the same stuff. Just a light coat is all you need. I have used it on fuel lines and hoses and even exhaust hangers and rubber bushings. a tube will last long enough that you forget all the swear words you used to have to use for the same job.
