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Thread: regular ,mid grade or premium fuel ….FYI

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    regular ,mid grade or premium fuel ….FYI

    in case you are wondering

    you may have to rewind the vid to the very beginning .




    Last edited by upflyer; 06-29-2015 at 01:35 AM.

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    I try to use premium from a top-tier rated brand. Not necessarily because it is a higher octane, but because it is loaded with more detergents (I know at least Shell and Conoco load their premiums with more). It's overkill, but on a 8 gallon fillup it isn't like the price difference is going to make me broke.

    Also, different countries and even states in the USA have different laws regarding formulation, sometimes the premium does not contain ethanol etc...
    Last edited by db1980; 06-29-2015 at 07:20 PM.

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    I'm not even sure I agree with his "high octane blows up with higher pressure" statement.

    Higher pressure earlier is what causes knock.

    Think of gunpowder, high octane is like slower burning powder, it burns slower providing higher pressure over a longer period of time.

    Lower octane is like faster burning powder, quicker burning over a shorter period of time.

    Higher octane is less susceptible to preignition which is too much pressure too early in the power stroke.

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    Scotty Kilmer is wrong on a lot of stuff.

    There is no "higher pressure" with premium fuel. It's less resistant to knock. MOST modern vehicles (the Mirage is definitely one) will see at least a minute improvement when running premium; If you have a vehicle requiring 87 you will never see a big enough increase in fuel economy to pay for premium unless you have something direct injection and higher compression or turbo-direct injection.

    Most modern vehicles are programmed to advance the timing as far as possible until knock. The computer can get a few more degrees on premium fuel over 87, but it won't be too big of an increase in fuel economy or power to make it worth it.

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    Quote Originally Posted by M-88 View Post
    Scotty Kilmer is wrong on a lot of stuff.

    There is no "higher pressure" with premium fuel. It's less resistant to knock. MOST modern vehicles (the Mirage is definitely one) will see at least a minute improvement when running premium; If you have a vehicle requiring 87 you will never see a big enough increase in fuel economy to pay for premium unless you have something direct injection and higher compression or turbo-direct injection.

    Most modern vehicles are programmed to advance the timing as far as possible until knock. The computer can get a few more degrees on premium fuel over 87, but it won't be too big of an increase in fuel economy or power to make it worth it.
    I agree wholeheartedly. The maximum amount of advancement that might be programmed into the engine management system probably is only a few degrees. More than likely there is a much broader range of timing retardation to allow for poor quality fuel so that engine damage doesn't occur during operation. Especially considering that the Mirage is mainly marketed in developing countries where quality fuel is a major issue.

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    X2.. x2..
    Mirage was designed to run very well on lesser grade fuels and will never pay back the cost of premium fuel with increased mileage. Putting premium in is throwing away money.
    Will weld for beer.

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    Quote Originally Posted by IchabodCrane View Post
    X2.. x2..
    Mirage was designed to run very well on lesser grade fuels and will never pay back the cost of premium fuel with increased mileage. Putting premium in is throwing away money.
    If you are doing it thinking you are going to make the cost up in efficiency, I agree. I don't necessarily agree with the last statement that putting premium in is throwing away money. I am making a conscious choice to use premium exclusively for the reason of higher detergent levels as I mentioned. It's just a piece of mind thing, may or may not have a tangible benefit, but I plan on keeping the car long term. If I were planning on ditching it after 5 years, I would probably just use the cheapest gas I could. I sort of look at it the same as washing, waxing, vacuuming...things that will cost money but not give you any performance/mileage benefit...you could call that all throwing money away, but I don't.

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    If you're just looking for detergent/cleaning action, use ethanol blended regular. Ethanol is one of the more powerful cleaners out there. Ethanol will keep everything spotless from the filler neck onward.

    No.. I'm not arguing with you, I'm just adding more information.
    Last edited by IchabodCrane; 07-01-2015 at 03:29 PM.
    Will weld for beer.

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        click to view fuel log View my fuel log 2014 Mirage SE 1.2 automatic: 45.3 mpg (US) ... 19.3 km/L ... 5.2 L/100 km ... 54.5 mpg (Imp)


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    Quote Originally Posted by IchabodCrane View Post
    If you're just looking for detergent/cleaning action, use ethanol blended regular. Ethanol is one of the more powerful cleaners out there. Ethanol will keep everything spotless from the filler neck onward.

    No.. I'm not arguing with you, I'm just adding more information.
    Well, I have to say I have no choice in that, I live in front range of CO, and all grades are E10. So yeah like I said, Its overkill, but I like the warm fuzzy feelings. Maybe I am throwing money away, but I do know its not going to give me better mileage, power etc. I know first hand that ethanol is a great cleaner, I stuck a tank of E85 into an old subaru and promptly clogged up my fuel filter from all the crud it loosened up. It did run great after that though lol.

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    Everyone always refers to the mirage being sold in foreign countries to explain how it's set to run weak gasoline, but I believe all small countries that are getting the mirage have a map sensor and a different ecu, American/Canadian mirages may not have the same ability to run excellent on poor quality gasoline and those designed for third world countries... Just a thought.


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