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
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
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.
That would be interesting to read. If you find a link, post it or email it,
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.
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.
The sulfur content has more to do with the crude than the brand. Since all
the refineries take from different wells at different times, it is not
possible to say a particular brand is exactly the same nation wide. Aside
from that, the gas in the tank is not always from the refinery whose name is
on the sign.
A very few people say they can tell the difference, but I never cold. Over
the years, I may have had a tank or two that did not seem up to snuff, but
going back to the same station a couple of weeks later, no problem. I buy
where it is convenient and the price reasonable. Not worth driving 20 miles
to save two cents a gallon.
Here are some sulfur-related excerpts from one of the sources I found:
"Effective on January 1, 2006, the per-gallon sulfur cap for gasoline
produced at most refineries dropped to 80 ppm. This standard does not
apply to all gasoline because there are different regulations for small
refiners and for refineries in the Rocky Mountain area."
"On January 1, 2004, the first phase of the EPA low sulfur gasoline
regulations were effective. The phase-in of these standards was
completed in 2006 for most refineries and importers. In 2006,
specifications for gasoline content changed from the previous 500 ppm
sulfur ceiling for RFG outside of California to a required 30 ppm annual
average and a per-gallon cap of 80 ppm for most gasoline (with some
delays for gasoline produced in the Rocky Mountain area or produced by
The rest of the article can be found at:
You can believe whomever you choose. If you believe a mechanic knows
more about gasoline chemistry and engine combustion than the chemists
and engineers, that is your call.
It is becoming more apparent that your real mission here is to make a
political statement about sulphur content of gasolines than to know what
is best for your engine.
What a load of crap! Heck, I know more about cars than a lot of the
monkeys I've met who work on them. The automotive business is rife with
folklore, myth and outright stupidity that passes for fact. Yes, there
are certainly intelligent, well educated mechanics that I know and
trust, but the fact that someone works on cars is no indication that
they understand anything about fuel chemistry or what happens inside an
engine. That doesn't mean they can't repair them, but it does make their
advice suspect. I repair computers all the time and I'm certified to do
so, but I couldn't tell you how a CPU works internally.
Have you ever heard of Google? Try searching on "sulfur content in
gasoline" and you'll get more information than you know what to do with,
much of it from government regulatory agencies. Quit being so lazy and
don't give us any more crap about there not being good information
available on the Internet. If you really believe that, why are you here?
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