Honda Car Forum

I have heard several theories on gas tanks....
.....never let the gas tank get almost empty.
.....always fill up before the tank is 1/4 full.
.....always use a fuel injector cleaner every dozen tanks.
.....fuel injector cleaners are worthless.

Anyone got any theorys/advice?

--

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"Bubba got a blowjob, BU$H screwed us all!" - Slim
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VOTE HIM OUT! November 4, 2004

||....never let the gas tank get almost empty.
||....always fill up before the tank is 1/4 full.

Almost all modern cars have a fuel pump immersed in the fuel tank, with the
motor above the pickup point. When it gets low, the motor can be partially
uncovered. Since the motor is cooled by the fuel running through it and around
it, it can run hotter if the fuel level is very low. Habitually running the
tank to the last drop can shorten the life of the pump.
The best way to kill a pump, is to park on a steep slope when the fuel level
is low, uncovering the pump and pickup. It won't start. By the time it dawns on
you to let the car roll down onto the flat, you have already damaged the motor
by letting it run without coolant/lubrication during the dry cranking attempts.
It will probably start once you get it on level ground, but it's days are then
numbered.

Texas Parts Guy

slim wrote:

>
> I have heard several theories on gas tanks....
> ....never let the gas tank get almost empty.

Not a good idea to run the fuel pump dry.

> ....always fill up before the tank is 1/4 full.

I'll just say a full tank is generally good. More air in
the tank may increase condensation. I think there's also
a greater likelihood of varnish in the tank with more
oxygen.

> ....always use a fuel injector cleaner every dozen tanks.

I do, but a good quality gas is probably "good enough".

> ....fuel injector cleaners are worthless.

They work to varying degrees. Techron Concentrate is
supposedly quite good, although others swear by Redline
SI-1 or BG 44K.

> Anyone got any theorys/advice?
>

Rex B wrote:
>
> ||....never let the gas tank get almost empty.
> ||....always fill up before the tank is 1/4 full.
>
> Almost all modern cars have a fuel pump immersed in the fuel tank, with the
> motor above the pickup point. When it gets low, the motor can be partially
> uncovered. Since the motor is cooled by the fuel running through it and around
> it, it can run hotter if the fuel level is very low. Habitually running the
> tank to the last drop can shorten the life of the pump.

OK. I hardly ever drive the car to the point where the GAS light comes on,
and if it comes on when I am driving, I fill up.

Do you think that I am safe, or should I fill up when the tank is 1/4 full?

--

http://www.bushflash.com/thanks.html
"Bubba got a blowjob, BU$H screwed us all!" - Slim
http://www.worldmessenger.20m.com/weapons.html#wms
George "The AWOL President" Bush: http://www.awolbush.com/
WHY IRAQ?: http://www.angelfire.com/creep/gwbush/remindus.html
http://www.toostupidtobepresident.co...ickenhawks.htm


VOTE HIM OUT! November 4, 2004

On Wed, 23 Jun 2004 04:53:14 GMT, slim <pickin's@nyc.rr.com> wrote:

||
||
||Rex B wrote:
||>
||> ||....never let the gas tank get almost empty.
||> ||....always fill up before the tank is 1/4 full.
||>
||> Almost all modern cars have a fuel pump immersed in the fuel tank, with the
||> motor above the pickup point. When it gets low, the motor can be partially
||> uncovered. Since the motor is cooled by the fuel running through it and
around
||> it, it can run hotter if the fuel level is very low. Habitually running the
||> tank to the last drop can shorten the life of the pump.
||
||OK. I hardly ever drive the car to the point where the GAS light comes on,
||and if it comes on when I am driving, I fill up.
||
||Do you think that I am safe, or should I fill up when the tank is 1/4 full?

Without knowing the specifics of your car, and seeing the way the pump is
positioned with respect to the sensor for the light, I would not have a clue.
Err to the side of caution, and try to fill up at the 1/4 mark.
Texas Parts Guy

"Rex B" <NOSPAMrex@REMOVEtxol.net> wrote
> Almost all modern cars have a fuel pump immersed in the fuel tank, with the
> motor above the pickup point. When it gets low, the motor can be partially
> uncovered. Since the motor is cooled by the fuel running through it and
around
> it, it can run hotter if the fuel level is very low.

Let's assume that the fuel pump and motor assembly design is such that gasoline
is circulated within the assembly casing and around the motor, to cool the
motor, in the gasoline's path from assembly inlet to outlet. (I haven't
confirmed this yet, so I'm going to make this assumption for now.) In this case,
all that is necessary to ensure this alleged 'motor cooling flow' continues is
for the assembly's inlet to be below the gasoline level in the tank.

For reference on this, drawings of a fuel pump in a fuel tank for a 1996 Civic
appear at

http://www.honda.co.uk/owner/CivicManual/pdf/11-87.pdf

http://tinyurl.com/2flnq (Majestic site)

> Habitually running the
> tank to the last drop can shorten the life of the pump.

I'm not buying it. Have any citations that discuss the motor-pump assembly
operation?

> The best way to kill a pump, is to park on a steep slope when the fuel
level
> is low, uncovering the pump and pickup. It won't start. By the time it dawns
on
> you to let the car roll down onto the flat, you have already damaged the motor
> by letting it run without coolant/lubrication during the dry cranking
attempts.

The condition you describe is the same as running out of gas.

So you're claiming that a few starts of the engine (and so fuel pump-motor
assembly) on an empty tank will destroy the assembly?

> It will probably start once you get it on level ground, but it's days are then
> numbered.

I suppose starting a car on an empty tank may reduce the life of the fuel
pump-motor assembly, but I'm doubtful, for now, that the reduction is
noticeable.

Citations welcome.

I think the original poster is perfectly safe continuing to drive such that the
gas warning light hardly ever comes on. If it does come on, and he/she fills up
right away, I remain confident that the system is designed so that no damage
occurs.

It would be a pretty silly design for the gas warning light to come on right as
damage starts occurring. Some margin of safety surely is built in.

I do like y_p_w's theory about a full tank tending to prevent condensation etc.
buildup. I've seen this discussed before. E.g. from the Car Talk guys re winter
driving:

http://www.cartalk.com/content/features/WinterDriving/
---
Keep your gas tank close to full, for a couple of reasons.
In the summer, you can take a chance and run down to fumes. But in the winter,
if you do get stuck or stranded, the engine will be your only source of heat.
And you don't want to have to worry about conserving fuel and saving the planet
right at that moment...you want to stay warm. (And make sure you keep a window
open a crack if you're sitting there with the engine running. We can't afford to
lose any listeners from carbon monoxide asphyxiation.)

The other reason for a full tank is that warm daytime temperatures will fill the
empty space in the tank with moisture, which will condense during the cold
night. This water will sink to the bottom and, sooner or later, rust out your
tank.
---

They amend this somewhat at
http://cartalk.com/content/columns/A.../March/02.html , noting that they
have seen less and less gas line freezes (due to condensation buildup, due to
too much air in the gas tank and not enough gas) over the years.

(Tom & Ray owned a garage together for a number of years. One of them still
works a full-time job at his garage.)

"slim" <pickin's@nyc.rr.com> wrote
> ....always use a fuel injector cleaner every dozen tanks.
> ....fuel injector cleaners are worthless.

I'd sure welcome any citations people have on fuel injector cleaners improving
engine lifetime and performance.

I think popular sentiment leans toward Chevron Techron. It's only about $6 a
bottle and preferably is used about every oil change.

After 152k miles, my 1991 Civic was getting great mileage (40+ MPG) as long as I
kept the PCV valve clear. It would clog up a bit about every two tanks of gas. I
never used a fuel injector cleaner or any other additive. I buy only regular
gasoline and am not picky about where I buy it.

Someone else reported recently that after 200k miles his Acura's PCV valve was
the original and had never fouled. Into the car he puts only "Esso/ExxonMobil
gas, whic is laden with MMT. Regular in the winter, premium in the summer."

For the first time a few weeks ago I put a bottle of Chevron Techron in my car's
full gas tank. I'm not certain yet but after one tank of gas my rough impression
is the PCV valve is staying cleaner longer.

Man, I would love to be able to get a few starts and maybe a little mileage
out of an empty tank

"> So you're claiming that a few starts of the engine (and so fuel
pump-motor
> assembly) on an empty tank will destroy the assembly?
>
> > It will probably start once you get it on level ground, but it's days
are then
> > numbered.
>



Starting a car on empy, have you thought about submitting this as an
alternative fuel source

Hugh "The phrasing was good for a few chuckles" Graham

> I suppose starting a car on an empty tank may reduce the life of the fuel
> pump-motor assembly, but I'm doubtful, for now, that the reduction is
> noticeable.
>
> Citations welcome.
>
> I think the original poster is perfectly safe continuing to drive such
that the
> gas warning light hardly ever comes on. If it does come on, and he/she
fills up
> right away, I remain confident that the system is designed so that no
damage
> occurs.
>
> It would be a pretty silly design for the gas warning light to come on
right as
> damage starts occurring. Some margin of safety surely is built in.
>
> I do like y_p_w's theory about a full tank tending to prevent condensation
etc.
> buildup. I've seen this discussed before. E.g. from the Car Talk guys re
winter
> driving:
>
> http://www.cartalk.com/content/features/WinterDriving/
> ---
> Keep your gas tank close to full, for a couple of reasons.
> In the summer, you can take a chance and run down to fumes. But in the
winter,
> if you do get stuck or stranded, the engine will be your only source of
heat.
> And you don't want to have to worry about conserving fuel and saving the
planet
> right at that moment...you want to stay warm. (And make sure you keep a
window
> open a crack if you're sitting there with the engine running. We can't
afford to
> lose any listeners from carbon monoxide asphyxiation.)
>
> The other reason for a full tank is that warm daytime temperatures will
fill the
> empty space in the tank with moisture, which will condense during the cold
> night. This water will sink to the bottom and, sooner or later, rust out
your
> tank.
> ---
>
> They amend this somewhat at
> http://cartalk.com/content/columns/A.../March/02.html , noting
that they
> have seen less and less gas line freezes (due to condensation buildup, due
to
> too much air in the gas tank and not enough gas) over the years.
>
> (Tom & Ray owned a garage together for a number of years. One of them
still
> works a full-time job at his garage.)
>
>

"Hugh Graham" <mattdalt@yahoo.com> wrote
C wrote:
> "> So you're claiming that a few starts of the engine (and so fuel
> pump-motor
> > assembly) on an empty tank will destroy the assembly?

> Starting a car on empy, have you thought about submitting this as an
> alternative fuel source

Hugh,

I am happy to make you aware that the starter motor, crankshaft, and DC-powered
fuel pump turn, and the spark plugs fire, when starting a car with no fuel in
the tank. If they didn't, there'd be no cause for concern.

Thank you for the chuckles. ;-)

On Wed, 23 Jun 2004 16:25:30 GMT, "Caroline" <caroline10027remove@earthlink.net>
wrote:


||> Habitually running the
||> tank to the last drop can shorten the life of the pump.
||
||I'm not buying it. Have any citations that discuss the motor-pump assembly
||operation?

Here's a start. A google search gets lots of hits.

http://www.alldata.com/techtips/2002/20020920d.html

Texas Parts Guy