Yeah, but that's for the idiots who can't figure that out on their own.
There's a ton of stuff in owner's manuals that shouldn't have to be said and
that pose no threat to the car.
Having said that, most in-tank pumps are cooled by the liquid in the tank
and it is advisable to keep the level above a quarter tank or so.
I'm still looking for some credible evidence that this is true.
Credible, means it doesn't come from AAA, or your brother-in-law, etc.
If it comes from a fuel pump manufacturer, fuel pump designer, car
maker, etc., I'd consider that reasonably credible. I've never yet
seen anything for any vehicle I've owned and, in fact, have some
evidence to the contrary. Admittedly, not a lot of evidence, but some.
First evidence is that I routinely run my vehicles down below 1/4 tank
or occasionally until the low fuel light comes on. I've run several
cars over 100K miles and have had only ONE electric fuel pump failure.
That was on a 96 Plymouth Grand Voyager that had in the neighborhood of
150,000 miles at the time of failure.
Second evidence comes from a guy who was a fuel pump designer for a
number of years and said that the fuel pumps are cooled by the gas they
are pumping (they pump the gas around the electric motor typically), not
the gas around them in the tank. It also comes from common sense.
Anyone with half a brain knows that moving a liquid past a source of
heat is much more effective for cooling than depending on relatively
still coolant. That is why cooling fans exist, why water pumps exist,
etc. Using the fuel around the fuel pump as coolant would be much less
effective as you'd be depending on the sloshing action alone to move
heat away from the pump. If the car is sitting still, this would not be
very effective. Pumping the coolant through the pump is the smart way
to do it, and the way every fuel pump I've seen has been designed. This
way, as long as the pump is running, a moving stream of coolant will exist.
That I cannot provide. Like you I dismiss the AAA suggestions and all of
the other completely unfounded stuff and do look for some credibility, or
some other assurance that the story is coming from a source that I can
trust. For the most part, I've been hearing this for a while now within the
auto-repair circles. From folks dealing with this stuff every day. I've
never heard a design engineer state it, or the manufacturer themselves, but
it is a concept that at least makes sense.
I've had a couple of GM pump failures. Like you, my cars stay in the family
for a long time. My failures have generally been upwards of 100,000 miles.
I make it a practice to keep 1/4 tank full but that's a longstanding habit
and a reflection of where I live. We are subject to condensation in the
tank and ice in the winter. Dry gas fixes this, but so does keeping a
sufficient level in the tank.
That was my reaction. When you have a choice to use gas just sloshing
around the pump or a constant stream of gas flowing through the pump, I
really believe that the design engineers are smart enough to choose the
latter. That doesn't rule out some cheap design from somewhere that
isn't well-designed, but I'm guessing that most quality conscious auto
makers would have eliminated those suppliers long ago.
Sure, you don't want to run out of fuel. Does the manual say that not
doing so will harm the fuel pump? I don't recall seeing that when I
read mine back in December.
Personally, I believe this is largely an urban legend. Maybe there are
some poorly designed electric fuel pumps out there, but most are cooled
by the fuel running through them, not the fuel they are immersed in.
So, as long as you have fuel, you have coolant for the fuel pump. And
once the fuel is gone ... the engine quits and there isn't much need for
the fuel pump then. :-)
This myth has been perpetuated by a lot of organizations who should know
better (AAA for one), but that doesn't make it true. AAA also says that
running low on gas will cause the pump to pick up sediment in the bottom
of the tank. Do they really believe that the fuel pickup, which is
located near the bottom of the tank, knows how much fuel is above it and
thus will only pick up sediment from the bottom when the fuel level is
low? Reading this sort of stuff is a hoot.
May be the point is that if you run with very few gasoline the pump could in
some moments to have cavitation picking up air bubbles instead of gasoline
and this is not good for lubrication inside the pump itself.
I have LPG on my Sonata and the LPG manifacturer recommends to keep in
gasoline tank at least 1/4 of capacity, even if I could run my engine
without any gasoline, using LPG.
I'm not familiar with LPG systems so I have no idea why that
recommendation. I just spent an hour reviewing the fuel system section
in the Sonata shop manual (official Hyunday manual set) and there is no
mention of keeping any minimum amount of fuel in the tank.
Remember, I specifically said credible sources. This is just another
person passing on the old wives tale. And even the grammar in this is
atrocious. I'm guessing this guy didn't make it past 8th grade.
I really like the "running completely out of fuel running out of fuel
allows the electric fuel pump to run "dry" which nearly immediately
ruins the pump." comment. I've run my Chevy pickup completely dry
several times (I used to carry a 50 gallon tank in the back to refuel my
airplane, so I always had gas available handily). My truck has nearly
100K miles on the original fuel pump. So much for the "immediately
ruins the pump" theory.
How gutsy do you feel? The most I ever pushed it was when it took 11.4
gallons to fill my, IIRC, 12 gallon tank in my 03 Accent. I don't
recall the distance I had driven, but it must have been close to 400
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