JohnH wrote:

Not a good idea to top off. Always leave some room for expansion. (Based
on
experience!)


Vapors expand and contract a lot. Liquid fuel expands a very little.
Built-in gas tanks in boats are vented. There will be more absorbtion of
water vapor during the vapor expansion/contraction cycles than with the tank
full of fuel.

That's what I think.

Eisboch