High octane gas on ELANTRA

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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.
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Mike Marlow wrote:

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

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.
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Matt Whiting wrote:

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.
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Matt Whiting wrote:

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.
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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.
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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.
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Edwin Pawlowski wrote:

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 small refiners)."
The rest of the article can be found at:
http://www.npra.org/issues/fuels/gasoline.cfm
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happy wrote:

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.
Matt
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happy wrote:

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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Anyone I've ever spoken to at Hyundai with an opinion on this has said that at best higher octane is a waste money and that it will likely cause more engine deposits.
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