"Magic" fuel additive - old gas?

peakbagger Posted By peakbagger, Jul 20, 2018 at 7:06 AM

  1. peakbagger

    peakbagger
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    I am seeing a consistently small increase in fuel mileage from burning up old gas. The background is a friend dropped off a Bronco that was sitting in covered storage since the year 2000. It had gas in it, but it stinks and looks quite brown like tea. I set aside 5 gallons and have been slowly pouring a quart or two every time I do a long trip. My car is ford fiesta with fuel injection and a digital fuel mileage readout that averages fuel flow versus mileage driven since its been reset. It doesnt have a turbo so probably no knock sensor.

    The really odd thing is I see a consistent increase in mileage by a couple or tenths to a half a mile per gallon. I usually do very long business day trips of 400 to 450 miles. I add the old fuel before the start of the trip and then refill the tank before heading home. its pretty consistent that the mileage will drop back a couple of tenths when I drive home after diluting the original tank and if I do not dose it as I am in rush and do another trip without adding the old gas, the mileage drops back a few more tenths and it stabilizes.

    This is definitely not a scientific study but is pretty consistent. I use cruse control pretty consistently and usually set it pretty consistently.

    My speculation. Year 2000 gas is probably non ethanol and may have some additives like MBTE that are now banned. Any volatiles had long since gone out the tank vents so what is in the tank is the lower fractions of what once were gas. In theory this has a high btu content along the lack of ethanol. I am adding a quart or two to a roughly 10 gallon tank so I could just be raising overall btu content.

    I thought the old gas may be acting like octane booster but since there is most likely no knock sensor this discounts the octane theory.

    Once I get rid of this old fuel, I may try to blend in small amounts of non ethanol gas to see if I get the same effect.

    Note I only do this on long trips to minimize potential injector clogging.

    So anyone care to speculate?
     
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  2. moey

    moey
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    Youll should get higher mpg from non ethanol gas as you mentioned. Your cost per mpg is what you want to look at when considering using non ethanol vs ethanol gas in a car not mpg alone.

    I think I would put the old gas in my mower before my car though.
     
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  3. zrock

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    your looking for trouble putting that old gas in your car. It will start plugging things up no matter how much you dilute it. I would not even put it in my lawn mower.
     
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  4. Highbeam

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    Your car almost certainly does have a knock sensor. All of my gas engines have had them as far back as 1996. Your timing can be automatically advanced without detonation if the old gas has the effect of adding octane or otherwise slowing combustion.

    I am not afraid of old gas at all. Unless it is full of water or mud. I might be more inclined to burn it full strength in a lawn mower though!
     
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  5. peakbagger

    peakbagger
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    Not worried in the least using old gas in small amounts on long trips. Back when EFI systems first came out the fuel suppliers didn't put in injector cleaning additive and plugged injectors were and issue. I used to buy Techron by the case for my Pontiac and ford mustang folks had issues with the 302 EFI system. These days I don't hear many issues with fouled injectors.

    I will have to take a look in my manual to see if a Fiesta has a knock sensor.
     
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  6. georgepds

    georgepds
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    The energy content of gasoline is higher than the energy content of gasoline cut with ethanol ( by volume). This observation is consistent with your results
     
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  7. Ashful

    Ashful
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    His Fiesta may have a smaller and less sophisticated motor than your mower, Highbeam. :p
     
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  8. blades

    blades
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    Heck if I could get away with running offroad diesel in my truck it would perform better also, problem isI do not know which LEO is colorblind.;lol
     
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  9. Highbeam

    Highbeam
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    I bought a lot of off-road diesel for machinery and always enjoyed the savings of about a dollar per gallon. The fine is very steep if you get caught using it on road and it’s not like you can switch back and forth, the dye leaves a stubborn residual.
     
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