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Discussion Starter · #1 ·
I heard from someone that the octane rating can drop anytime gas is transferred ie from tanker to gas station tank and from gas station tank to your car. Is there any truth to this? Also, is there a time period that the gas is good for in a container?<p>Given that the R is so octane sensitive, I have to wonder if maybe some stations have "stale" gas or maybe "watered down" gas.<br>
 

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Re: Octane rating Drop (Kirb)

Well, there's not really much truth there, but there are a couple of things that can happen to gas. <p>1) Moisture can work it's way into the gas as it ages. This is obviously not good. <p>2) If the gas has ethanol in it, the ethanol likes to go bond with water. If there is excessive moisture in any of the receiving tanks, the ethanol could come out of suspension and bond with the water, changing the chemical composition and dropping the octane rating. <p>3) If the gas sits in an open container, the higher order hydrocarbons will volatize off, changing the composition and lowering octane. <p>HOWEVER, all of the above is EXTREMELY insignificant and rare if you go to a station that has ANY volume at all. Most busy city stations get deliveries every 24-48 hours. Depending on the station, that means that they go through 5,000 to 25,000 gallons per day. Some popular stations off the highways even go through 40,000 GPD. <p>Also, any major gas station you go to does it's best to ensure that the tanks are tight, including atmospheric emissions. Therefore, the chances of volitazation happening are extremely rare. <p>Moisture making it in is somewhat more likely, but not very. Plus the connection between the truck and the tank is sealed (i.e. it's not just a hose in a hole like when you fill your tank) and there's not much chance of anything happening there. When you fill your tank, it's not really closed, but the volume of fuel going in vs. the relative area of air it contacts makes any volatization very very unlikely. <p>If you feel like you got a bad batch of gas, chances are it was contaminated in some way, rather than it was "old" or "stale"<p>Bottom line, if you don't keep cans in your garage or a tank at your house, and if you live in a relatively populated area with a relatively busy station, you're fine. If you put gas in a plastic container that was bone dry and very air tight, it would have a pretty long shelf life. In a more open container like a gas can for your lawn mower, yes, gas will have a shelf life. However, the moisture that makes it way in and the higher hydrocarbons that make their way out won't really matter to your lawn mower. But don't throw it in your car and expect it to run really well.
 

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Re: Octane rating Drop (Kirb)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD><i>Quote, originally posted by <b>Kirb</b> »</i></TD></TR><TR><TD CLASS="quote">Thanks for the great explanations!</TD></TR></TABLE><p>Kirby are you cheaping out and putting crappy gas in your R again!?! I thought we went over that!!! <IMG NAME="icon" SRC="http://www.vwvortex.com/vwbb/tongue.gif" BORDER="0"> <p>
 

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Discussion Starter · #5 ·
Re: Octane rating Drop (Kaizai)

Yep, still using Chevron 91 California craptane. $3.35/gallon. Ready to dunk some octane booster next fillup for the hell of it.
 

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Re: Octane rating Drop (Kirb)

Holy smokes! We're only paying ~$3.08/gal for 93 octane here. Though I'm sure the old saying "California leads and the rest of the country follows" will likely hold true here. <IMG NAME="icon" SRC="http://www.vwvortex.com/vwbb/rolleyes.gif" BORDER="0">
 

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Re: Octane rating Drop (R Salesman)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD><i>Quote, originally posted by <b>R Salesman</b> »</i></TD></TR><TR><TD CLASS="quote">Holy smokes! We're only paying ~$3.08/gal for 93 octane here. </TD></TR></TABLE><p><br>HAHA!! Yeah....."ONLY"<p><IMG NAME="icon" SRC="http://www.vwvortex.com/vwbb/biggrin.gif" BORDER="0">
 

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Re: Octane rating Drop (R Salesman)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD><i>Quote, originally posted by <b>R Salesman</b> »</i></TD></TR><TR><TD CLASS="quote">Holy smokes! We're only paying ~$3.08/gal for 93 octane here. Though I'm sure the old saying "California leads and the rest of the country follows" will likely hold true here. <IMG NAME="icon" SRC="http://www.vwvortex.com/vwbb/rolleyes.gif" BORDER="0"> </TD></TR></TABLE><p>Yeah, but we're also getting the "10%" mix year round now.<p> <IMG NAME="icon" SRC="http://********************/smile/emthdown.gif" BORDER="0">
 

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Re: Octane rating Drop (R Salesman)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD><i>Quote, originally posted by <b>R Salesman</b> »</i></TD></TR><TR><TD CLASS="quote">Holy smokes! We're only paying ~$3.08/gal for 93 octane here. Though I'm sure the old saying "California leads and the rest of the country follows" will likely hold true here. <IMG NAME="icon" SRC="http://www.vwvortex.com/vwbb/rolleyes.gif" BORDER="0"> </TD></TR></TABLE><br>I tend to doubt that you have California's tax structure on gasoline sales. They have to pay for all of the incentives they have put out for hybrid cars somehow.... Guess who gets hit? They even have a term for it - demand side management....
 

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Re: Octane rating Drop (needsdecaf)

I'm no gas expert, but if the more volatile HC's vapor off (lower chain lengths like pentane, hexane and septane, wouldn't the larger average molecule size SLOW the combustion rate and RAISE the "octane" rating?<p>Wasn't octane (C8H18) originally picked because is was the "ideal" in knock resistance (100% octane = 100 octane anti-knock rating). I know there's a lot of other stuff in gasoline (aromatics, etc.) besides simple<br>(CnH2n+2) straight chains (aren't those called paraffins?), but logic would suggest that getting rid of the most volatile would slow the burn rate and raise the knock resistance. Set me straight if that's wrong.
 

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Re: Octane rating Drop (Hi Alt R)

$3.49 for 91 at my local station today.
 

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Re: (23109VC)

Yea I just drove from Pheonix, AZ to LA and then home and I saw $3.79 for 91.
 

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Re: (Kaizai)

$3.09 for Shell 93 here in Dallas.
 

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Re: (TexasV70R)

Right now in my Audi A4 1.8T (V70 R is Mid-Atlantic right now...arriving Baltimore 24 May) I'm running a 25% Ethanol blend. All gasoline in MN is 10% Ethanol to begin with. So by putting 3 gallons of E-85 in my tank, and then filling up with standard premium for the rest, I'm getting a 25% blend. Because E-85 is around 105 Octane, I'm getting a full tank of 94.5 Octane gas at (for the last tank) $2.76 per gallon on average. E-85 is running between 40 and 60 cents cheaper per gallon than premium unleaded.<p>I've noticed no performance drop (my boost gauge still peaks at 20 [yes, the car is rather substantially modded]) and my fuel economy has dropped around 5% from running straight premium unleaded.<p>So I thought I'd just add some fuel to the fire of fuel talk. <IMG NAME="icon" SRC="http://www.vwvortex.com/vwbb/smile.gif" BORDER="0">
 

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Re: (Moneypenny)

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD><i>Quote, originally posted by <b>Moneypenny</b> »</i></TD></TR><TR><TD CLASS="quote">Right now in my Audi A4 1.8T (V70 R is Mid-Atlantic right now...arriving Baltimore 24 May) I'm running a 25% Ethanol blend. All gasoline in MN is 10% Ethanol to begin with. So by putting 3 gallons of E-85 in my tank, and then filling up with standard premium for the rest, I'm getting a 25% blend. Because E-85 is around 105 Octane, I'm getting a full tank of 94.5 Octane gas at (for the last tank) $2.76 per gallon on average. E-85 is running between 40 and 60 cents cheaper per gallon than premium unleaded.<p>I've noticed no performance drop (my boost gauge still peaks at 20 [yes, the car is rather substantially modded]) and my fuel economy has dropped around 5% from running straight premium unleaded.<br>So I thought I'd just add some fuel to the fire of fuel talk. <IMG NAME="icon" SRC="http://www.vwvortex.com/vwbb/smile.gif" BORDER="0"></TD></TR></TABLE><p>be careful, your fuel system might not like what the alcohol will do to the seals and such...E-85 compatible cars have fuel lines, seals and etc that are resistant to alcohol....<p><br>also, instead of octane booster, some 100 octane race gas, or even toluene or xylene do a better job than octane booster. most of the octane boosters will only raise the octane by a few points IE: 91 to 91.4 for "104" octane boost" IIRC, two gallons of xylene or tolune will raise octane level from 93 to 96.<br>your fuel lines might not like too much pure toluene or xylene either, but pump gas contains both within certain concentrations. make sure to add the toluene or xylene first then wash the filler tube out by topping off with pump gas.<p><br>
 
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