Don't Taze Me, Bro! wrote:
> Consider filling up your tank and not letting it drop below halfway, instead
> of keeping it on low and only putting in 2 gallons here and there...
>
> http://www.foxnews.com/story/0,2933,361347,00.html
>
> Not because you could run out of gas and get stranded but because repeatedly
> running on low tends to ruin the fuel pump.

I see that thing about running low on fuel damaging fuel pumps posted
all over the internet, but personally I think that's total b.s.

All the critical parts in the fuel pump - bearings (bushings), armature,
brushes/commutator, pumping elements (vanes, rotors, or rollers) - are
constantly bathed in the fuel as it flows thru the pump. That
lubricates and cools the parts regardless of fuel level in the tank.

With regulator bypass pumping/circulation that modern cars have, there
is full volume of fuel going thru the pump at all times it is running
regardless of engine demand. The only effect of low fuel in the tank is
a slight temperature rise of the volume of fuel in the tank (due to same
electrical power dissipated in the pump being absorbed by less mass of
fuel), and that rise will be very small - power used by fuel pump is
small - temperature rise of the fuel in the tank and the tank itself
will be very small - lots of mass compared to the power being dissipated.

*BUT* - again - the fuel is constantly flowing thru and around all
internal components of the pump whenever it is running providing cooling
(unless you actually run out and the engine stops - but that is a
different scenario altogether, and even then, the pump will still be
full of fuel at that point with a full column of fuel from its lowest
end to the fuel rail - only the pickup will be filled with air, and
there won't be any flow - and most cars turn the pump off when the
computer senses that the engine is no longer running).

If anyone wants to argue this, be sure of your facts beforehand - I used
to design automotive fuel pump components.

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
address with the letter 'x')