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Discussion Starter #1
I was wondering around when I came across this thread.
Effects of different fuels on NA engine power

One of the posters "Power-Tripp" made a statement that fresh fuel is key.
With pump gas I would tend to agree only because of there's no way to really know how long the fuel has been stored in the underground tanks.

What about sealed five gallon containers is it considered fresh?
 

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Just Some Dude in Jersey
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I'll jump in here with my own question: For Winter storage and only once every week or two engine running to keep the battery charged, would high test gas stay "fresher" longer than regular? By that I mean: Will higher octane gas maintain the minimum amount of volatility needed for a decent chance at starting and running the engine a tad longer than plain ole regular?
 

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Opeler
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What about sealed five gallon containers is it considered fresh?
Are you referring to a plastic 5 gallon container that you fill with fuel, or one you purchase that comes sealed with the foil top that you have to peel back after you remove the screw on cap? Either way, fuel has a shelf life, PERIOD. The five gallon "can" made out of plastic will preserve fuel pretty well for a couple months, up to around 4 or so months in my own experience. Have not actually seen any sold in individual sealed five gallon containers, but would think if you could find it that way, you should be able to see at least 6 to 9 months out of that type of sealed container. The problem with fuels is they are a mixture, with additives that stabilize the fuel so that it will last for at least 3 months. Most fuel stocks are turned over in that time without issue in most markets. The only way I have found to prevent fuel related issue's is to add Stabil to the fuel you purchase for items that you have a need to store for any length of time. If you do not add stabilizer, the VOC's evaporate from the fuel (yes, even fuel in sealed plastic containers will degrade in time) and that's when you start having problems with varnishing and other aged related fuel issue's. The newer blends of fuels are even worse in my experience. I also DO NOT buy ANY ethanol or oxygenated fuels for storage purposes as they seem the MOST problematic for storage purposes. I always buy one hundred percent (or as close as you can get anymore) fuel and add Stabil as per the instructions and that will prevent fuel issues for up to a year or slightly more. Stinks sumtin fierce when you actually run the engine with that mix, but it will run and not be problematic.

" Will higher octane gas maintain the minimum amount of volatility needed for a decent chance at starting and running the engine a tad longer than plain ole regular"

Actually, no, the VOC's leave the "better" fuels faster, and thus create problems sooner, at least, IN MY EXPERIENCE on the subject. I always buy just regular ole 87 octane and add Stabil. I have had "high quality, high octane fuels" go bad in a matter of a month or so, but have had 87 octane with Stabil still start and run without issue in a given engine after 1 and a half years. Of course this will depend entirely on the fuel available to you and how you treat it and store it. Ideal is a cool dark place in a sealed plastic container with some form of stabilizer. Simple as that.:yup:
 

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Detritus Maximus
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I really don't trust any fuel after a few months. It's not so much the degradation of performance, but the likelihood of crud settling out and clogging things. My GT is really finicky about the age and quality of the fuel (no matter what octane). It has trouble starting after just a couple months. My Safari van, on the other hand, starts no matter what. It sat for a year and a half with fuel that was a couple months old already and fired right up. A few months back I had to drain 5 gallons of 1 year old nasty brown fuel out of the GT. I filtered it to get the particles out and ran it thru my lawnmower. I could tell the difference, but it burned it.
 

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Opeler
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Gasoline is a mixture of straight chain paraffins (pentane, hexane, heptane, octane etc. low octane), branched paraffins (iso-octane, etc., higher octane), aromatics (toluene, xylenes, etc. (v. high octane), olefins, cyclic parafins, and oxygenates (alcohol, ETBE, etc.). The difference between summer and winter blend is the Reid Vapor pressure, winter blend has more volatile butane and pentane making starting easier. When stored these low molecular weight volatiles will vaporize into the head space of the container and be lost every time the can is opened. If the seal is not tight and if the can experience any thermal changes, the light ends will leak out due to pressure differentials. The light aromatics also are quite volatile, hence will be distilled out over time thus reducing the octane rating. In addition oxygen leaks into the container, thus allowing the olefins and other radicals to become oxidized. This can form the varnishes and sediment. Oxidation also leads to the formation of peroxides which lower the octane rating. Some polymerization may also occur where two molecules may join to form a larger molecule that plates out onto surfaces. The alcohol is hygroscopic, hence will attract water.
 

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Über Genius
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Here is my experience on fuel. Specifically gasoline or Petrol as those "other" people call it.

If you have NO oxygen getting to the fuel it will stay usable for a VERY long time. In a sealed drum you can count on years.
In a vented gas tank it will stay usable for a couple months. After six months you might as well get a pump and pump it out. BUT, if you can get a car running on six month old gas it can get amazing fuel economy (OK, this isn't a fact but with bad gas I ONCE got over 50 MPG in my Mustang with a 5.0 and no I'm not exagerating)

Gas will go bad faster as the temperature warms up. 3 months in 100 degrees is the same as 9 months at 35 as for the gas deteriorating.

If you DO want to try to freshen up old gas, the more you dilute it with good gas the better you will be. You can freshen it up even better with aviation gas (100 octane).
Add a little (couple ounces per gallon) isopropyl and a little acetone and it will help get rid of some of the varnish you get with old gas.

This advice is for OLD cars, not newer FI engines.
 
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