Any benefit to 91 octane?
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Thread: Any benefit to 91 octane?

  1. #1
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    Any benefit to 91 octane?

    The title mostly says it all. I know the engine is designed to work on 87, but, I was curious if the ECU would be able to take advantage of more octane? A few more horses or slightly better gas mileage perhaps? My friend has a 2011 Camaro 2SS that can run on 87, but loses 40hp, so it got me wondering. Not that I expect something that dramatic.

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    Forgot to put in the title, this is for the SX turbo.

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    12/2011 ROTM linsfreak's Avatar
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    Quote Originally Posted by mornen View Post
    Forgot to put in the title, this is for the SX turbo.
    Not sure how big the turbos on these cars are...but my last car obviously gas/air mixture is the most important thing. My blower was about 18lbs a boost which im sure is not close to the kia. My advice, if you raise the boost on that turbo in whatever way, you will need more gas for sure with good ignition meaning spark. So in my opinion higher octane would do nothing but waste money.

    Just my thoughts

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    Higher octane fuel doesn't buy you anything at all in performance and may actually reduce fuel efficiency in an engine designed for lower octane levels. I'm sure the recommended fuel for your friends Camero is at least 92 octane. Higher compression ratios require higher octane fuel to operate efficiently and prevent knocking. GDI is a newer technology that's more comparable to diesel than it is to MPFI engines. I don't think you'd see any difference at all using high octane fuel except a reduction in your bank balance.

  6. #5
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    I agree, higher octane is a waste of money. Octane is a resistance to knocking, i.e. a resistance to igniting prematurely and causing a knock and maybe punch a hole in your piston. This is needed for higher compression engines as the fuel can be ignited by the temperature caused by the compression rather than just by the spark ignition. While the GDI engine is relatively high in compression it is rated for 87 octane.

    Also all the extra detergents and cool stuff the premium brands and high octanes boast about do little for the GDI engine as the fuel is sprayed directly into the combustion chamber rather than the manifold before the valves. Therefore all the great stuff that cleans the valves would never touch them.

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    The other posters are correct. You will see absolutely no advantage whatsoever from using higher octane than the engine was designed for.

    Most modern engines that require premium (92 octane) have built-in knock sensors to prevent doing permanent damage to the engine if someone puts in 87. The horsepower of the engine will be reduced as a result. Some even advertise that you can use either for this reason, but the power will be lower (for example, the Hyundai 4.6L V-8 gives power figures for both 87 and 92 octane).

    However, the 2.4L and 2.0L turbocharged engines in the Optima were designed for 87, not 92. Using higher octane will only waste money.

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    Quote Originally Posted by ZXnVS View Post
    The other posters are correct. You will see absolutely no advantage whatsoever from using higher octane than the engine was designed for.

    Most modern engines that require premium (92 octane) have built-in knock sensors to prevent doing permanent damage to the engine if someone puts in 87. The horsepower of the engine will be reduced as a result. Some even advertise that you can use either for this reason, but the power will be lower (for example, the Hyundai 4.6L V-8 gives power figures for both 87 and 92 octane).

    However, the 2.4L and 2.0L turbocharged engines in the Optima were designed for 87, not 92. Using higher octane will only waste money.
    Development tests for the new mill included 300 hours at wide-open throttle, followed by 20 hours of operation at 6,700 rpm (the rev limiter is set at 6,600 rpm in the car). While the durability testing included 87 octane fuel, engineers hint that the calibration of the 2.0T will automatically take advantage of higher octane on premium fuel, peak horsepower goes up by about 10. And although peak torque is unaffected by the addition of premium fuel, the area of torque curve before the peak is said to plump up somewhat.

    Taken from Edmunds Insideline:
    2011 Hyundai Sonata 2.0T First Drive

  9. #8
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    Quote Originally Posted by in2tv@hotmail.com View Post
    Development tests for the new mill included 300 hours at wide-open throttle, followed by 20 hours of operation at 6,700 rpm (the rev limiter is set at 6,600 rpm in the car). While the durability testing included 87 octane fuel, engineers hint that the calibration of the 2.0T will automatically take advantage of higher octane on premium fuel, peak horsepower goes up by about 10. And although peak torque is unaffected by the addition of premium fuel, the area of torque curve before the peak is said to plump up somewhat.

    Taken from Edmunds Insideline:
    2011 Hyundai Sonata 2.0T First Drive
    Early reports by Kia stated that you can gain 10 horsepower by running premium in a 2.0. Have not personally tried premium - anyone out there that can speak from experience?
    Tech and Premium Packaged SX - - He who dies with the most toys wins!!

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    Thanks in2tv@hotmail.com and thedad1234 for your responses.

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    The 4.6L V-8 in the Hyundai Genesis was specifically designed to use both types of fuel, and they even give horsepower figures for 92 octane and for 87. I find it very hard to believe that they would design the 2.0T engine for premium and not say a word about it, except to "hint" to one writer (out of dozens of reviews that I've read) that it will gain 10 HP on premium.

    I'm not saying it's not true, but it will take something much less dodgy than one writer's claim that an engineer "hinted" this to him to make me believe it.
    Last edited by ZXnVS; 04-17-2011 at 04:12 PM. Reason: typo

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