Best lube for grey tank and black tank valves

I like the idea above, but it would be nice to better understand the exact location of the screw lubrication hole.

Another thing to consider is always avoid the ethylene glycol rv antifreeze which is cheaper and causes the rubber valves to dry out because of its alcohol content.

You want to look for the propylene glycol rv antifreeze which will help the valves little bit with lube.