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Thread: Octane rating vs. fuel mileage which is best?

  1. #21
    Senior Member Ares's Avatar
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    Thing about the ecoboosts is that they are a gas saver compared to the v6 when idling - OR before you hit boost. As soon as you hit boost, bye bye mpg.

    I did love all the driving dynamics of the escape though. Tight suspension, nice steering feel and steering ratio, peppy for a 2.0.

    Hell, I wanted to take one of the bigger ecoboost engine AWD autocrossing...



  2. #22
    Senior Member GrnBn's Avatar
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    For everyone trying to argue that the cost of using premium fuel is so prohibitive that, even were there gains we should avoid them, have you actually done the math on this? The difference from 87/89 to 91/93 is literally cents. Do some napkin math on how much fuel you actually consume in a year and you'll find that this switch probably adds less than $100 to the amount you'll spend on gas. I'm not advocating we all run premium, or race gas, or pure ethanol, or anything really. I just get irked hearing that argument from people for whom premium fuel really is necessary, like owners of turbocharged vehicles or fancy high compression motors, so hearing it on here was like AGH

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    Here the premium is 10 cents more per liter, not worth it ...

        __________________________________________

        click to view fuel log View my fuel log 2014 Mirage ES 1.2 manual: 40.8 mpg (US) ... 17.4 km/L ... 5.8 L/100 km ... 49.0 mpg (Imp)


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    Quote Originally Posted by GrnBn View Post
    For everyone trying to argue that the cost of using premium fuel is so prohibitive that, even were there gains we should avoid them, have you actually done the math on this? The difference from 87/89 to 91/93 is literally cents. Do some napkin math on how much fuel you actually consume in a year and you'll find that this switch probably adds less than $100 to the amount you'll spend on gas. I'm not advocating we all run premium, or race gas, or pure ethanol, or anything really. I just get irked hearing that argument from people for whom premium fuel really is necessary, like owners of turbocharged vehicles or fancy high compression motors, so hearing it on here was like AGH

    On my parents escape:

    Fuel cost for 100 miles on 87 octane $15.8031
    Fuel cost for 100 miles on 91 octane $15.8031

    I think the 91 octane may be a ten-thousandths or two more expensive ...

    The vehicle does run much better and doesn't have to downshift all the time so they run 91 all the time.

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    Senior Member GrnBn's Avatar
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    Again, if you got significantly different responses from your motor you might feel differently. I don't believe for our cars it will have an affect without modifying the intake/exhaust and tuning, but for other vehicles it can make a substantial change and is definitely worth the ten cent difference.

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    91cavgt (01-28-2016)

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    I am new here from the Geo Metro forum. My GF just bought a Mirage when her old car went south based on my research of these cars.

    Anyway, here is my opinion of fuel from personal experience. AVOID AVOID AVOID Caseys gas if you have this where you live. It is cheap but not good. Poor power and fuel economy are the best case. Detonation and pinging are also a possibility.

    My parents bought a 1996 Chevy S-10 with the 2.2L inline 4 when I was growing up. This thing was a total dog and I can't imagine it with an automatic transmission. The one we had was a manual and was told it was pretty much the way to go if you get one of these. It barely had enough power to pull itself around. Being a teenager, I wanted to see if there were any ways to pep it up a bit. It called for 87 octane in the manual. I tried 89 octane and was pleasantly surprised that it ran smoother and had more power by the seat of the pants. So since the 89 was an improvement, I assumed that going to 93 would be even better. I was mistaken and the truck was even more of a dud than it was with 87. I found it was best to alternate between 87 and 89 octane with this truck. I am not sure if this was the most economical way to do it but the truck ran well and had the most power with this combination. Keep in mind NOTHING was changed from stock. The intake and tuning were never touched.

    I find that mixing about 30% e85 fuel into the tank of the Geo Metro brings increased performance but not economy. I mainly do this to keep combustion chambers/valves clean in one of my cars that uses a little oil.

    The Mirage came with a full tank of gas from the dealer and I am sure they didn't spend more on anything above regular which is 87 octane where we live. It got 50mpg on the way home and seemed to pull the uphill grades without an issue. This is with a new engine that likely isn't fully broken in by the way.

    Altitude also plays a role in naturally aspirated cars. You don't need as high of an octane at higher elevations. Alcohol boosts octane but reduces mileage. Some don't like alcohol in their gas but it does absorb moisture as well as help clean the fuel system so I don't mind a tad.

    Experiment and see what works best for you.

    Conor

  9. #27
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    @cwatkin

    If you want to keep engine clean buy Top Tier gas. It has x3 times more cleaning detergents of EPA requirement. More info at http://www.toptiergas.com

    It may be slightly more expensive (though in my area it is same price or cheaper) and is good insurance for your engine.

    GasBuddy smart phone app and website mark TT stations, so they are easy to find good luck!
    https://m.gasbuddy.com/

        __________________________________________

        click to view fuel log View my fuel log 2015 Mirage DE 1.2 manual: 46.4 mpg (US) ... 19.7 km/L ... 5.1 L/100 km ... 55.7 mpg (Imp)


  10. #28
    Senior Member Cobrajet's Avatar
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    Quote Originally Posted by cyclopathic View Post
    @cwatkin

    If you want to keep engine clean buy Top Tier gas. It has x3 times more cleaning detergents of EPA requirement. More info at http://www.toptiergas.com

    It may be slightly more expensive (though in my area it is same price or cheaper) and is good insurance for your engine.

    GasBuddy smart phone app and website mark TT stations, so they are easy to find good luck!
    https://m.gasbuddy.com/
    I always run Top Tier 87 octane, with 10% crappy ethanol. Usually run either Arco or Chevron. Before you say it, Arco has been Top Tier since 2014. I'd love to find some ethanol-free gas around here, but the only places it is available are unattended card-lock type places and I almost always pay cash.

    I have tried different octanes in different vehicles and have come to the conclusion that if the car ain't designed for high-octane, high-octane ain't worth buying. But there is a night-and-day difference in my BMW between 87 and 91 (it's designed for 91).

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    Quote Originally Posted by Cobrajet View Post
    I always run Top Tier 87 octane, with 10% crappy ethanol.
    I wish I could use E85 here. Have you ever seen the documentary "Pump"? I highly suggest it. I'm wondering if anyone has tried running their Mirage on ethanol.

  12. #30
    Senior Member Cobrajet's Avatar
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    Quote Originally Posted by nickpon View Post
    I wish I could use E85 here. Have you ever seen the documentary "Pump"? I highly suggest it. I'm wondering if anyone has tried running their Mirage on ethanol.
    Mirages are not 'flex fuel' vehicles, as cars designed for E85 are called here in the States. When E10 first appeared here in the 1990s I thought it was a pretty cool idea. But the whole corn-as-a-motor-fuel experiment has been a complete waste. I hope ethanol-laced gasoline goes away, but since it's really little more than a political gift to to the Corn Lobby (to keep corn prices high) I doubt it will.

    I'd love to be able to find pure gas again.



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