I have a Les Paul Standard that is about 19 years old, and I've never touched the truss rod in all that time. I decided to try a heaver gauge of strings, which required a truss rod adjustment. I bought a 5/16 truss rod wrench for use with Gibsons, but I can't get the truss rod to turn. Do you think it is because the truss rod hasn't been touched for so long? Could I put something like wd40 on it to loosen it up? Or, could the truss rod adjustment be maxed out? Here's the best picture I could get of the truss rod nut:
