Re the HALF FULL rule:  Is the decreased fuel economy (from dragging around that
extra fuel), compensated for the lessening of the fuel evaporation??

Or conversely:

Does the lessening of the fuel evaporation make up for the lost fuel economy
from dragging around the extra fuel  in the FULL tank?

John:  I realize that you are just forwarding the interesting post.  m

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From: John Rodgers <inua@CHARTER.NET>

    TIPS ON PUMPING GAS

    One of the most important tips is to fill up when your gas tank is
HALF FULL. The reason for this is the more gas you have in your tank the
less air occupying its empty space. Gasoline evaporates faster than you
can imagine.