High octane gas on ELANTRA

[Matt Whiting]

Water and dirt and other debris.

This is an issue even if the tank is half full as water and most debris
is heavier than gasoline and sinks to the bottom anyway.

Tanks rusting from the inside out is another issue. Plastic fuel tanks
have ended that.

What does tank rusting have to do with running near empty?

Fuel also acts as coolant for the in-tank fuel pumps. Run it dry
enough and the pump will overheat and possibly wear faster.

Yes, we've discused this hear before. I believe this is an OWT, but
many still believe it. I don't know if hyundaitech has ever weighed in
on this one though? How about it hyundaitech, does Hyundai have any
official word on fuel pump cooling/life as a function of running the
tank near empty?

Matt

 

[Edwin Pawlowski]

Yes, we've discused this hear before. I believe this is an OWT, but many
still believe it.

It has come up on other groups also. You are right about the OWT. Many
have brought it up, but no one has actually given any evidence.

 

[PMDR]

What does tank rusting have to do with running near empty?

Assuming the tank is rusting inside, once the fuel level drops, more
surface will be exposed to air, oxidize, and produce loose particles
and debris.

This happened to car in my extended family. It was always driven with
less than a quarter tank of fuel to save weight and eventually the tank
rusted from the inside out and sent debris through the fuel lines and
clogged the fuel filter.

Yes, we've discused this hear before. I believe this is an OWT,

I am pretty sure I've read that in more than one owners manual.

 

[Matt Whiting]

Assuming the tank is rusting inside, once the fuel level drops, more
surface will be exposed to air, oxidize, and produce loose particles
and debris.

This happened to car in my extended family. It was always driven with
less than a quarter tank of fuel to save weight and eventually the tank
rusted from the inside out and sent debris through the fuel lines and
clogged the fuel filter.

With a modern closed system, you should not have air in the tank above
the fuel, only fuel vapor.

I am pretty sure I've read that in more than one owners manual.

I've owned more than 10 cars in 32 years and have never seen this once
in an official source. If you can post even one make/model and page
number in the manual, I'd much appreciate it.

Matt

 

[Mike Marlow]

With a modern closed system, you should not have air in the tank above
the fuel, only fuel vapor.

Not sure I can go with this one Matt. Cars do not have a means of depleting
air from the gas tank. They have the means to control the pressure in the
tank relative to atmospheric pressure, but not the gases that make up that
pressure. There is no way to remove the oxygen (even the levels typical of
the air we breath) in a gas tank, thus oxidation is not only possible in a
metal gas tank, but common.

I'm not so sure though, how much of a problem oxidation from within the tank
really is though. I believe more of the issues with contaminants inside the
tank are from those contaminants being pumped into the tank at the gas
station.

 

[Matt Whiting]

Not sure I can go with this one Matt. Cars do not have a means of depleting
air from the gas tank. They have the means to control the pressure in the
tank relative to atmospheric pressure, but not the gases that make up that
pressure. There is no way to remove the oxygen (even the levels typical of
the air we breath) in a gas tank, thus oxidation is not only possible in a
metal gas tank, but common.

I'm not so sure though, how much of a problem oxidation from within the tank
really is though. I believe more of the issues with contaminants inside the
tank are from those contaminants being pumped into the tank at the gas
station.

I can't find a reference at the moment, but I remember reading that one
reason that there isn't an explosion concern with in-tank electric fuel
pumps is that the tank has only liquid gasoline and gasoline vapor and
not enough oxygen to support combustion or explosion. The explanation
was that the charcoal canister traps excess gasoline vapor which is them
drawn back into the tank as the fuel is depleted. Proper operation of
this system requires the gas cap to be tightly in place hence the fact
that most modern cars (I think OBD II and later) will light the MIL
indicator.

And, as I've mentioned previously, I run my cars down to 1/8 tank (until
the light comes on) quite often and I've never had a tank rust out and
have had only one electric fuel pump fail and that was after about
150,000 miles so I don't think it was a failure due to overheating of
the pump due to lack of gas in the tank as that would happen much sooner
than 9 years and 150K miles.


Matt

 

[Mike Marlow]

I can't find a reference at the moment, but I remember reading that one
reason that there isn't an explosion concern with in-tank electric fuel
pumps is that the tank has only liquid gasoline and gasoline vapor and
not enough oxygen to support combustion or explosion. The explanation
was that the charcoal canister traps excess gasoline vapor which is them
drawn back into the tank as the fuel is depleted.

That would be interesting to read. If you find a link, post it or email it,
will ya?

And, as I've mentioned previously, I run my cars down to 1/8 tank (until
the light comes on) quite often and I've never had a tank rust out and
have had only one electric fuel pump fail and that was after about
150,000 miles so I don't think it was a failure due to overheating of
the pump due to lack of gas in the tank as that would happen much sooner
than 9 years and 150K miles.

I've never lost a fuel pump and I've driven my cars over 200K. I have lost
a couple of tanks though, to rust. It appeared to be from the inside out,
at the seams. These were all on GM's, but that's because except for the
wife's Hyundai, GM's are pretty much all that have graced our garage. I do
know of a lot of folks who have had tanks rot out on Fords as well. I don't
admit to knowing people who own Chrysler products.

 

[Brian Nystrom]

I don't think it is a problem even with regular gasoline since the EPA
started requiring vapor recovery systems.

Moisture still gets into the tank due to condensation. Air has to be
allowed into the tank as it drains and it brings moisture in with it.

 

[Brian Nystrom]

With a modern closed system, you should not have air in the tank above
the fuel, only fuel vapor.

For that to be true, you'd have to have a vacuum in the tank. It simply
doesn't work that way. As the fuel level in the tank falls, air is drawn
in to replace it. There is no alternative.

 

[Brian Nystrom]

I can't find a reference at the moment, but I remember reading that one
reason that there isn't an explosion concern with in-tank electric fuel
pumps is that the tank has only liquid gasoline and gasoline vapor and
not enough oxygen to support combustion or explosion. The explanation
was that the charcoal canister traps excess gasoline vapor which is them
drawn back into the tank as the fuel is depleted. Proper operation of
this system requires the gas cap to be tightly in place hence the fact
that most modern cars (I think OBD II and later) will light the MIL
indicator.

That's simply impossible. Yes, fuel vapor trapped in the carbon canister
is drawn back into the tank along with outside air. The fuel is adsorbed
by the carbon, then released as air is drawn through it and into the
tank. There is no way to not have outside air entering the tank. To have
a completely sealed system, you would have to pressurize and
depressurize it as you add and subtract fuel from the tank. Fuel systems
in cars don't work that way.

 

[Mike Marlow]

For that to be true, you'd have to have a vacuum in the tank. It simply
doesn't work that way. As the fuel level in the tank falls, air is drawn
in to replace it. There is no alternative.

Correct. If the vacuum existed as described, one would not be able to
remove the gas cap, and all of our vehicles would share a common attribute
with Jaguars - caved in gas tanks.