I have done many tasks in service to The Mistress - 77 XJC - and her predecessors, but I’ve never changed out the gasket on a gas tank sump plug. While feeling fortunate? lucky? that it’s just the gasket and not a tank replacement, my question is, does the plug go in dry or should I smear a gas proof sealant on the threads? I’m changing out the vague tank level float on that side at the same time. The Haynes manual is obtuse on this point.

Use HYLOMAR BLUE on both sides of the rubber seal, you don't need much, just a very thin coat of the stuff.

I found Haynes to confuse me more than it helped me. I believe that useful information is there. but, the organization hides it. Seems that it is a copy of jaguar publications. Originaly Series I and II. then a section on series IIi cars was crudely grafted in...

It is in my shed.... Have not looked at it for over a decade.

I removed those sump plugs a decade or so ago. I reeinstalled them dry. No leaks..