Repeatedly Running On A Low Tank?

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Old 02 Jun 2008, 06:12 am   #1 (permalink)
Don't Taze Me, Bro!
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Default Repeatedly Running On A Low Tank?

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.


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Old 02 Jun 2008, 06:28 am   #2 (permalink)
mjc13
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Default Re: Repeatedly Running On A Low Tank?

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.
>
>


While Fox "News" might on occasion slip and let a fact slip through
their filters, I wouldn't count on it. We've been running our cars down
to 1/4 or even 1/8 of a tank on a regular basis for 25 years, and have
never had a fuel pump fail. I just sold my 1986 Civic Si with the
original pump. It's much more important to replace the fuel filter at
the recommended interval.
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Old 02 Jun 2008, 06:34 am   #3 (permalink)
Bill Putney
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Default Re: Repeatedly Running On A Low Tank?

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')
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Old 02 Jun 2008, 06:44 am   #4 (permalink)
Elmo P. Shagnasty
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Default Re: Repeatedly Running On A Low Tank?

In article <%HP0k.6360$%Z1.4068@trnddc05>,
"Don't Taze Me, Bro!" <N00One187@NoWhere.Com> 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.


Um, no it won't.

Interesting that the article just threw that out there with no further
explanation. But then, that's Fox News for you.

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Old 02 Jun 2008, 07:22 am   #5 (permalink)
Enrico Fermi
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Default Re: Repeatedly Running On A Low Tank?


"Don't Taze Me, Bro!" <N00One187@NoWhere.Com> wrote in message
news:%HP0k.6360$%Z1.4068@trnddc05...
> 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.

It's like every "factual" story in the media is just all spin. So, is this
guy an Oil Company shill trying to get us to fill-up and inflate the price
of gasoline? A futures trader? A tow-truck operator? An idiot? It could be
anything but the truth. There is so much unadulterated BS in the media, from
NAFTA Superhighways to infomercials for Jack LaLanne Juicers. The Reader's
Digest used to be the main source of of this righteous nonsense (That's
Outrageous!) but now it is everywhere. Do you awaken with a painful need to
urinate? You need a new drug! Do your too-small briefs leave red marks on
your skin? It's cancer! My favorites are the ads for Lunesta: Side effects
many include drowsiness! WTF? Sorry for the rant...........


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Old 02 Jun 2008, 08:00 am   #6 (permalink)
C. E. White
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Default Re: Repeatedly Running On A Low Tank?


"Bill Putney" <bptn@kinez.net> wrote in message
news:6ai0kvF37k2jlU1@mid.individual.net...
> 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')


As I understand it this concern mostly applies to older systems that
included a return line, not more modern systems that use returnless
systems and variable delivery pumps. The concern is that continually
running with low fuel levels can lead to the fuel temperatures
becoming much hotter than desirable. Older systems with a return line
pumped much more fuel than necessary to the engine compartment -
particularly during low speed / low power operation. The excess fuel
is diverted back to the pump at the pressure regulator under the hood
through the return line. However, this process of pumping the fuel to
the front of the car, through the hot engine compartment, and through
the pressure regulator heats the fuel. With a full tank, the warmer
fuel being returned to the tank only changes the overall temperature
of the fuel in the tank slightly. However, when the tank is nearly
empty, the hot fuel coming from the return line has a much greater
effect on the average temperature of the fuel in the tank. Repeatedly
running the tank with low fuel levels results in a much higher average
fuel temperature, particularly in hot climates. Higher pump operating
temperatures can shorten the life of the pump. I can't say how much
hotter the fuel can get, or how much this can shorten the life of the
pump, but I do understand the theory. I suspect it was much more of a
problem 20 years ago than now. I know my Sister, a chronic low tank
driver, had to replace two in-tank fuel pumps on her mid 80's car, but
her late 90's car never had a problem.

And even if the fuel never get so hot so as to contribute to a pump
failure directly, running around with very low fuel levels can lead to
running out of fuel altogether, which is definitely not good for the
fuel pump.

Here are some interesting references:

http://findarticles.com/p/articles/m...07/ai_n8795921
http://www.autocarepronews.com/defau...=art&id=82095&
http://www.athomemechanic.com/archiv...your_fuel.html
http://answers.yahoo.com/question/in...3130941AATbVqN

Ed

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Old 02 Jun 2008, 08:53 am   #7 (permalink)
jim beam
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Default Re: Repeatedly Running On A Low Tank?

Enrico Fermi wrote:
> "Don't Taze Me, Bro!" <N00One187@NoWhere.Com> wrote in message
> news:%HP0k.6360$%Z1.4068@trnddc05...
>> 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.

> It's like every "factual" story in the media is just all spin. So, is this
> guy an Oil Company shill trying to get us to fill-up and inflate the price
> of gasoline?


no, that could /never/ happen. not ever. not in a million bajillion
years. no sir.

oh, wait, the fuel pump thing is utter bullshit, so...



> A futures trader? A tow-truck operator? An idiot? It could be
> anything but the truth. There is so much unadulterated BS in the media, from
> NAFTA Superhighways to infomercials for Jack LaLanne Juicers. The Reader's
> Digest used to be the main source of of this righteous nonsense (That's
> Outrageous!) but now it is everywhere. Do you awaken with a painful need to
> urinate? You need a new drug! Do your too-small briefs leave red marks on
> your skin? It's cancer! My favorites are the ads for Lunesta: Side effects
> many include drowsiness! WTF? Sorry for the rant...........

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Old 02 Jun 2008, 09:14 am   #8 (permalink)
C. E. White
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Default Re: Repeatedly Running On A Low Tank?


"Enrico Fermi" <noone@nowhere.com> wrote in message
news:HJQ0k.4185$jI5.3049@flpi148.ffdc.sbc.com...
>
> "Don't Taze Me, Bro!" <N00One187@NoWhere.Com> wrote in message
> news:%HP0k.6360$%Z1.4068@trnddc05...
>> 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.


> It's like every "factual" story in the media is just all spin. So,
> is this guy an Oil Company shill trying to get us to fill-up and
> inflate the price of gasoline? A futures trader?


This angle actually could have some validity. Back during the gasoline
crisis of the 70's, related to the Arab oil embargo, I heard it
claimed that one of the factors that caused the shortage was public
hysteria. Instead of the average car running around with a half a tank
of gas, people suddenly tried to keep their tanks near full. This
caused a surge in demand, which made the shortage far worse.

I can see where someone speculating in gasoline futures would like to
encourage people to increase the amount of gas they are buying in the
short run to keep the demand up long enough so that they can get out
with a big fat profit. However, if you are following this strategy,
you need to get out before people revert to old habits...

Ed

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Old 02 Jun 2008, 10:32 am   #9 (permalink)
hachiroku
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Default Re: Repeatedly Running On A Low Tank?

On Mon, 02 Jun 2008 09:14:43 -0400, C. E. White wrote:

>> It's like every "factual" story in the media is just all spin. So,
>> is this guy an Oil Company shill trying to get us to fill-up and
>> inflate the price of gasoline? A futures trader?

>
> This angle actually could have some validity. Back during the gasoline
> crisis of the 70's, related to the Arab oil embargo, I heard it
> claimed that one of the factors that caused the shortage was public
> hysteria. Instead of the average car running around with a half a tank
> of gas, people suddenly tried to keep their tanks near full. This
> caused a surge in demand, which made the shortage far worse.



I had a friend who would run his tank near empty all the time. He would
stop and put in $2 every so often just to keep the car running.

I always kept my tank near full all the time (still do).
I stop and put in (now, $6) every so often.

What's the difference?

(HINT: What happens when either one of us runs out of money?)



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Old 02 Jun 2008, 10:35 am   #10 (permalink)
hachiroku
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Default Re: Repeatedly Running On A Low Tank?

On Mon, 02 Jun 2008 05:53:18 -0700, jim beam wrote:

>> It's like every "factual" story in the media is just all spin. So, is this
>> guy an Oil Company shill trying to get us to fill-up and inflate the price
>> of gasoline?

>
> no, that could /never/ happen. not ever. not in a million bajillion
> years. no sir.
>
> oh, wait, the fuel pump thing is utter bullshit, so...



Once again you show how little you know.

The fuel pump is cooled by fuel. If you run on a low tank that doesn't
cover the fuel pump, it can fail prematurely. At $190~425 for a fuel pump.
it's probably cheaper to keep enough fuel in the tank to cool the pump.

What did I expect from someone who changes his oil at 12,000 miles whether
it needs it or not.

Reply when you get a clue...


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