Anyone use regular gas in their Si?

  1. AUGM1

    AUGM1 Member

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    Just wonder how the performance and gas mileage are affected.
     
  2. Honda_RacerX

    Honda_RacerX Senior Member

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    Itll run like poop.
     
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  3. Masked

    Masked Senior Member

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    Oof big no for me, I'm on 94 and nothing less. This platform performs super well on higher octane gas, don't go below 91.
     
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  4. REBELXSi

    REBELXSi Señor Member

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    I've done it over a full tank of highway miles and it was fine but I was just cruising the whole time. Didn't see a hit on mpg.

    I wouldn't do it if I was going to drive in a... Spirited fashion.
     
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  5. Jayceegee

    Jayceegee Senior Member

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    Uhhhh, no on regular gas
     
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  6. Bluecoupe777

    Bluecoupe777 Member

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    Just my two cents..Honda recommends premium in the turbocharged Si for a reason. I would never recommend putting regular in a car that is designed to run on premium fuel unless you want to risk some type of future repair work. Also, I'm pretty sure it says either premium fuel only/required or at the very minimum, recommended right inside the fuel door as a reminder. I'd also think this could potentially void the warranty on the engine should something go wrong from running 87.
     
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  7. tinyman392

    tinyman392 Senior Member

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    Required fuel is regular unleaded with premium recommended. So using regular fuel won't void the warranty, but it'll pull timing and cut power to adjust for the different fuel. Basically with the Si (and Type R), the engine is designed to run on premium, but can run on regular as well with an ECU that will adjust timing for the fuel that is in it.
     
  8. Gino27

    Gino27 Red Rocket

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    Sometimes I put 87 in it just by habit. The power doesn't feel as smooth as with 93, but a lot of people would be totally fun with just regular.
     
  9. REBELXSi

    REBELXSi Señor Member

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    They definitely won't void the warranty for using regular. It says premium recommended.

    If you want the full potential of the engine, stick to premium.

    You could probably go far on regular gas and Honda fluids but this is a forum of mostly enthusiasts so there's a lot of synthetic oil from boutique manufacturers and definitely no regular gas.
     
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  10. MattyNice

    MattyNice Senior Member

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    Yeah, it says “recommended” I believe for cars with sport mode. I just figure I bought the car for the performance so may as well use high Tess. I have thought about using 87 at times but even my cheap *** has yet to do it.
     
  11. pinhead66

    pinhead66 Member

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    My first tank from the dealer was 87. After that nothing but 91. If you drive it conservatively all the time im sure 87 would be more cost effective. But since the gas mileage is so great theres no reason to skimp.
     
  12. LittleturboSi

    LittleturboSi Member

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    Yes I did that on purpose few times to test. The performance is affected by using 87, but not by much as I thought relatively (vs 2015 Si). The mileage is about 6-8% worst for the same type of driving.

    For my 2015 Si, I could tell the difference right away even between 89 and 91.
     
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  13. Monocacy

    Monocacy Senior Member

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    Yes, that is about what I found. Modern engines have knock sensors so if your engine begins to knock under load the computer will adjust the timing, reducing knock but also reducing fuel efficiency. Increased fuel efficency for high-octane gas partially offsets the increased cost of high-octane fuel.

    Also, knock sensors don't adjust timing until they hear knock. Over time knock increases wear and tear on your engine.

    For me it does not make sense to buy a sporty car and then not give the engine the fuel needed to perform as designed.
     
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  14. ltrinh

    ltrinh Senior Member

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    Since dealer had 87 in the tank, I used 87 for the first 1k miles, then 91 (there is no 93 in SoCal) for the next 1k miles, back to 87 for the next 1k miles. Obviously this was for testing. 87 performed slightly worse in MPG, but not by much, as expected.
    91 is better for the engine, more fun, and MPG. Enough for me to stick to 91 ever since the first 3k miles testing.
     
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  15. maggs_10thgen

    maggs_10thgen Senior Member

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    Premium fuel is very important in a turbo charged vehicle. You want to avoid detonation.
     
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