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Gas Octane

Discussion in '2nd Gen. Tacomas (2005-2015)' started by BreezyTaco, May 9, 2009.

?

Which fuel octane do you use?

  1. 87

    2,148 vote(s)
    64.6%
  2. 89

    449 vote(s)
    13.5%
  3. 91

    764 vote(s)
    23.0%
  4. Other fuel additives

    55 vote(s)
    1.7%
  1. Jan 8, 2013 at 6:34 AM
    #861
    Creemore

    Creemore Well-Known Member

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    Ethanol level and octane ratings are independent things.

    It so happens that some fuel companies - Shell, for example - don't use ethanol in their premium grade (a marketing decision). For some people, buying this kind of premium is a way to avoid ethanol.

    It also so happens that ethanol naturally makes fuel less inclined to detonate, so some fuel companies actually rely on it to increase their octane rating (largely a marketing trick, in my opinion, since not every car that likes a higher octane rating likes ethanol). Sunoco Ultra 94 is an example of a gasoline that uses ethanol to raise its number.

    That's why there's always so much confusion around the ethanol/octane question.
     
  2. Jan 8, 2013 at 7:27 AM
    #862
    B11

    B11 Well-Known Member

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    My boat has a 8.1L (496ci) owners manual says 89 unless running fuel that has 10% Ethanol, if running fuel with 10%, 91 octane is recommended.

    If Ethanol doesn't change fuel, for the worse, why do I need to run a higher octane fuel if it has Ethanol in it????
     
  3. Jan 8, 2013 at 7:45 AM
    #863
    Creemore

    Creemore Well-Known Member

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    I don't know, but I'll share an experience I had that might be an example of how that could be: Some years ago, I went to replace the exhaust system on my Bimmer. I had run Ultra 94 in it exclusively, reasoning (wrongly) that higher octane is better no matter how high you go. Where I live, Ultra 94 has ethanol in it. The exhaust pipe was always black and sooty, but I never gave it much thought because the car was new and under warranty. My mechanic told me that they had had a number of BMWs in the shop for running rich, and the reason turned out to be that BMW's knock sensors 'heard' ethanol combustion as pre-detonation and retarded the timing/enriched the mixture to compensate. After the new exhaust went on, I switched to V Power which has a lower octane rating but, around here, has no ethanol. I sold that car years later with not a spec of soot in the exhaust pipe.

    Ethanol does change fuel. It lowers its energy content a little bit, and theoretically raises its octane rating a little bit (though not always in a useful way).

    Does your boat engine have an ECU that works like the one in a car? If not, it may simply run dirtier with ethanol, and higher octane will prevent detonation of unburned fuel as the plugs foul over time.
     
  4. Jan 8, 2013 at 8:49 AM
    #864
    B11

    B11 Well-Known Member

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    My boat, 2006 Cobalt, has an ECU and a knock sensor.

    I know Ethanol blended fuel absorbs moisture much more rapidly than does straight gas and that because blended fuels absorb water quicker/easier it deteriorates/lowers the fuel quality and octane much faster.

    Here is a link to a site that helps you find pure, unblended, gas in your area. They even have and App.

    http://pure-gas.org/

    Also, here is some good "Gasoline vs Ethanol" information.

    When you pull up to a gas pump to buy gasoline, are you aware that what comes out of the pump can vary with the seasons of the year? Is not Gasoline gas? The US government formulates the gas for seasonal changes; summer and winter. One US gallon of gasoline contains 114,000 BTU of energy; depending on the time of year, and depending on what is in the gasoline. It is getting harder to find gasoline's that does not contain 5 to 10% of Ethanol. Ethanol is ethyl alcohol; the kind of alcohol in beverages; beer, whiskey, bourbon, vodka, cocktails, etc.. It takes one and a half US gallons of ethanol to equal the energy in one US gallon of gasoline; the reason... because ethanol only has 76,100 BTU's of energy per gallon. Less energy means less miles per gallon. In 2007 George W. Bush made it possible for gas stations to sell Gasohol (E10) without labeling the pumps; in other words, you may not know alcohol is in the gas. Ever wonder where your gas mileage went?
    Gasoline's blended with Ethanol will lower MPG in most engines. The EPA says Fuel efficiency can decrease by 1.5 to 3% but reports of 40 % are not unheard of. In winter, you get less mileage out of a tank of gas; we waste a lot of gas warming up our vehicles, but what about trips? Winter gasoline contains less BTUs per gallon, 112, 500; if you are using 100% gasoline (non-ethanol). A lot of States no longer sell 100% gasoline it at the pumps. They choose Ethanol in the gasoline as a way to meet the Clean Air Act emissions standard. If you have a vehicle that was made before 1990, it is most likely not compatible with alcohol in fuels. Alcohol deteriorates the gaskets and seals that touch the fuel will fail. Alcohol affects the engines timing; makes the engine work harder. Many engine manufacturers prohibit the use of alcohol in the fuel; it is not just cars and trucks; industrial engines, generators, lawnmowers, weed eaters; all gasoline powered engines are affected.
    It is the BTUs that allows us to get the best fuel economy. Adding alcohol, of any kind, to gasoline, dilutes the fuel and lowers the heat energy. The pumps provide us a choice of Octane's. The higher the octane rating, the less chance there is of pre-ignition. Octane has nothing to do with the BTU energy content of the gasoline, so use what your engine manufacturer recommends.
    Non-ethanol (100%) gasoline is available, but it is getting hard to find. Marinas and aviation fueling stations still carry it because boat and airplane engines require it. Alcohol absorbs water, and water can cause damage.

    Gasoline Gallon Equivalent
    calculated based on 114,000 BTU's of energy per gallon Reference
    FuelGGEBTU/unitGasoline (base)1 US gallon114,000 BTU/galGasoline (conventional, summer)0.996 US gallon114,500 BTU/galGasoline (conventional, winter)1.013 US gallons112,500 BTU/galGasoline (reformulated gasoline, ETBE)1.019 US gallons111,811 BTU/galGasoline (reformulated gasoline, MTBE)1.020 US gallons111,745 BTU/galGasoline (10% MBTE)1.02 US gallons112,000 BTU/galGasoline (regular unleaded)1 US gallon114,100 BTU/gal Diesel #20.88 US gallon129,500 BTU/galBiodiesel (B100)0.96 US gallon118,300 BTU/galBiodiesel (B20)0.90 US gallon127,250 BTU/galLiquid natural gas (LNG)1.52 US gallons75,000 BTU/galCompressed natural gas (CNG)126.67 cu ft900 BTU/cu ftHydrogen by weight0.997 kg119.9 MJ/kgLiquefied petroleum gas (LPG)1.35 US gallons84,300 BTU/galMethanol fuel (M100)2.01 US gallons56,800 BTU/galEthanol fuel (E100)1.5 US gallons76,100 BTU/galEthanol (E85)1.39 US gallons81,800 BTU/galEthanol (E10)1.019 US gallons111,836 BTU/galJet fuel (naphtha) 0.97 US gallons118,700 BTU/galJet fuel (kerosene)0.90 US gallons128,100 BTU/galElectricity33.40 kilowatt-hours3,413 BTU/(kW-h)
    States that "do not" require ethanol/alcohol pump labeling:
    DC, Indiana, Kansas, Kentucky, Maryland, Michigan, Minnesota, Missouri, Nevada, New Hampshire, New Jersey, North Carolina, Ohio The following States may require labeling; dependent on percent of ethanol in the fuel:
    Alabama, Arizona, Arkansas, Colorado, Connecticut, Delaware, Georgia, Hawaii, Idaho, Illinois, Iowa, Louisiana, Massachusetts, Mississippi, Montana, Nebraska, New Hampshire, New Mexico, New York, North Dakota, Oklahoma, Oregon, Rhode Island, South Carolina, South Dakota, Tennessee, Texas, Utah, Vermont, Virginia, Washington, West Virginia.
     
  5. Jan 8, 2013 at 1:23 PM
    #865
    Yota4me

    Yota4me Active Member

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    I use 89 ethanol free fuel, Saw it from that awesome site pure-gas.org a couple months ago.
     
  6. Jan 9, 2013 at 6:54 AM
    #866
    oldstick

    oldstick Middle Age Member

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    It might be my imagination but seems like I can feel a very slight improvement in the smoothness during acceleration when I put the occaisional 89 or higher in the tank on my 07 V6. Can't prove it though.

    However, on the brands, I have become a believer in the additives used by the major brands in our area (mostly Chevron, Shell, Exxon). This was after my Dad was having trouble with his gas gage not reading so the Ford dealer told him it was a common problem, gas related and to pour in a can of Chevron Techron aditive and that fixed it immmediately.

    (Dad always buys the cheapest gas available, like those places where the concrete is always oily looking and the gas smells a little like diesel fuel.)
     
  7. Jan 9, 2013 at 1:17 PM
    #867
    ElTacoCaliente

    ElTacoCaliente Well-Known Member

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    I put 91 but, I use 93, can't find 91 anywhere around here.
     
  8. Jan 9, 2013 at 3:07 PM
    #868
    mlew

    mlew Member

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    I thought the computer would adjust the timing to prevent ping.
     
  9. Jan 9, 2013 at 4:12 PM
    #869
    P9HST2

    P9HST2 Well-Known Member

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    I believe it does up to a point. After that point, with low octane gas, it can't or won't compensate. That's my thoughts...
     
  10. Jan 9, 2013 at 6:01 PM
    #870
    DBTaco

    DBTaco Well-Known Member

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    I think my gas light was about to come on yesterday so i stopped at the shell and put 10 gallons of 93 premium in my truck. Usually i put the 87 grade of sheetz gas. Im not sure if its in my head or what but it seems that my truck ran smoother than usual. But i havent had my truck but a month so i dont know
     
  11. Jan 10, 2013 at 7:52 AM
    #871
    B11

    B11 Well-Known Member

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    Shell's premium gas used to be Ethanol free but now, it too, is a blended fuel. I think I did read that Shell Premium in Canada is still pure gas though.
     
  12. Feb 20, 2013 at 12:23 PM
    #872
    neonlazer

    neonlazer Mechanically Goofy

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    Ok I feel lazy to read this entire thread. Just found out anyone can buy gas next door and they sell ethanol free gas...so I assume I should get gas there from now on? :p
     
  13. Mar 11, 2013 at 7:25 PM
    #873
    cotaco05

    cotaco05 Well-Known Member

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    I've been running 85 and just put my first tank of 91 in (going to try it for 3-5 fill ups) to see if my mpg varies enough to save me a few bucks.
    Since filling with 91, I seem to notice the truck running "easier" on the freeway.
    Probably the same as it being faster after I wash it (all in my head)
     
  14. Mar 12, 2013 at 7:09 PM
    #874
    CantSitStill

    CantSitStill Well-Known Member

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    Since ScanGauge install;
    Same 60 mile trip that i make werkly, being very mindful to try to drive the same... No difference in MPG between 87 and 91

    91 only makes idle a bit smoother
     
  15. Mar 15, 2013 at 11:27 AM
    #875
    jhodge83

    jhodge83 Any dog under 50# is a cat and cats are useless... Staff Member

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    wat?
    it takes more than one tank for the ECU to adjust.
     
  16. Mar 15, 2013 at 11:28 AM
    #876
    dexterdog

    dexterdog My pee parts itch

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    Ethanol content can vary state to state beyond what is federally mandated.
     
  17. Apr 3, 2013 at 2:11 PM
    #877
    gwos25

    gwos25 Well-Known Member

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    I just towed a 6500 lb trailer over 3000 km in my 2012 dcsb, 6MT. Tracked my mileage along the way and tried prem vs reg to see if there was a difference. Here's what I noticed.
    Best recorded mileage was on regular, 11.4 mpg. Worse was 8.7, average over the whole trip was 10.5. After experimenting for awhile, I stuck with regular cause I couldn't stomach paying 1.50+ a liter for premium in northern ontario. I couldn't feel any difference in power using the prem. Now, the hp increase due to the elevation change from calgary to ontario was vastley apparent.
     
  18. Apr 8, 2013 at 2:29 PM
    #878
    Hammock

    Hammock Member

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    Up here in north Alberta, Shell's 91 is indeed ethanol free. Ethanol content is higher as the octane rating goes down.
     
  19. Apr 9, 2013 at 4:16 PM
    #879
    CASTRATE

    CASTRATE Well-Known Member

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    I ran 87 until recently. I figured I would give 91 a try, and noticed a smoother idle, slightly better mileage, and the truck feels like it has a little more umph when I goose it
     
  20. Apr 22, 2013 at 12:14 AM
    #880
    S.B.

    S.B. Well-Known Member

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    At this elevation (6000'+) I ran 85 loaf and jug gas (cheap stuff) and it started knocking when I got on it, so now I only use Shell 91 or chevron 91 (usually cause I fill up in Flagstaff on my way to cali). I hate knocking!

    In San Diego (before I came here to colorado) I used to run just 87.

    Even though this is kinda backward from what is supposed to happen: My truck is pickier in higher elevation then at sea level and it gets the best mileage with 91 vs. 85 or 89.
     
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