About to rust seal a fuel tank.  I've read where a little WD-40 on threads will prevent rust seal coverage. If I let rust seal cover the threads of the fill neck, would the gas cap still fit?

In general, for the very coarse threads of the filler neck, RustSeal is great for this application. 2 coats of RustSeal is roughly 5 mils thick and there should be enough tolerance in the coarse threads that the cap will still tighten nicely on the filler neck.

 

Please note: Prep the tank and threads with KBS Klean and RustBlast before applying the RustSeal. This allows for maximum adhesion and durability.

 

Please let us know if that helps and reach out if you have additional questions.