Anyone use regular gas in their Si?

  1. Dharmaboy

    Dharmaboy Senior Member

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    sweet. Guess all we have to worry about is oil dilution and swapping out the oil ever 3-5k Miles
     
  2. amirza786

    amirza786 Senior Member

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    Just follow the MM. Oil analysis on my last change after 7K of hard driving showed that I could have waited past 8K. Changing your oil every 3 to 5K is unnecessary, wasteful to the environment and doesn't help your wallet
     
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  3. Jolavemma

    Jolavemma Member

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    Please explain more . What scientific method or opinion ?
     
  4. amirza786

    amirza786 Senior Member

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    #109 amirza786, Sep 18, 2019
    Last edited: Sep 18, 2019
    Sure, let me start with the question: Would it be bad to go back and forth between 87 and 91? The scientific answer is NO. The reason is that 1) Premium is recommend and not required for this car and 2) when using Regular or Premium, the cars ECU will adjust timing based on what type of gas has been added in the tank by either pulling or advancing timing. This is documented, and I have seen it myself in data logs from when I did runs. You would see this under knock control or k.control. The reason for this is 87 octane is more volatile and can pre-ignite causing knock or ping in higher compression/turbo charged engines

    An opinion would be making the statement that switching between 87 and 91 is bad, the reason being is first of all its not correct and secondly there is no data to support that, from Honda or anywhere else. The person feels for whatever reason that switching back and forth would hurt the car without actually experiencing it being damaged.

    That being said, Premium is the recommended fuel, the car will perform better on it, and you will get 15 more hp, which is a good reason to use it.

    One caveat I would like to point out is if you are tuned, that changes the equation, as in most cases the car was specifically tuned for premium (Ktuner base maps, TSP Stage 1 tune etc)
     
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  5. Jolavemma

    Jolavemma Member

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    good to know ! Thank you very much for taking the time to explain it brother
     
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  6. amirza786

    amirza786 Senior Member

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    You are very welcome!
     
  7. j9lazur

    j9lazur New Member

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    I'm a new 2020 Si owner and am still on my first tank of gas. I found this old thread and want to add new info with this screen grab from the 2020 manual. It's similar to what has been said but a little more specific. If your car has sport mode, which the Si does, the manual is specifically recommending 91 octane or higher and cautioning against anything less than 87. Of course, if you never use sport mode, perhaps not an issue. Dunno.

    Screen Shot 2019-12-29 at 8.08.23 PM.png
     
  8. tinyman392

    tinyman392 Senior Member

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    The sport mode designation is talking about cars with sport mode vs sport mode itself (note how they say models with sport mode vs just sport mode, they are referring to the model vs the mode). So if you have a car with sport mode, then they recommend 91, minimum is 87, and anything lower than 87 can cause damage to the motor. The mode you're driving the car in doesn't matter in this case, it's the fact that it has the mode available. IE, if you're driving in normal mode using 85, you can damage your motor, but 91 is still recommended in normal and sport modes. I'm assuming they are using the sport mode designation to group together the following trims: Si coupe, Si sedan, Sport coupe, Sport Touring coupe, Sport sedan, and Sport Touring sedan instead of listing those 6 outright.

    TL;DR: The sport mode is used to indentify the model/trim of the vehicle not referring to the mode itself, rather a car having said mode. Using < 91 octane in normal mode may still cause knock, using < 87 octane in normal mode will cause damage.
     
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  9. AegeanT

    AegeanT Senior Member

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    Dealer put in regular on my first tank. Ran 89 midgrade for my 2nd/3rd tanks, and then just started to run premium on my 4th (current) tank after noticing the prices come down.

    I'll just say that I notice a decent difference between when I got the car with regular and on this tank with premium gas that I put in. It feels smoother and throttle response I find is a bit better.

    So as long as prices are reasonable, I will always put premium in. It's good to know (and I confirmed with dealer along with my manual) that running regular is fine if I have to though.
     
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  10. j9lazur

    j9lazur New Member

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    @tinyman392 thx, makes sense--there's a manual for sedans and one for coupes, each including all trim levels
     
  11. tinyman392

    tinyman392 Senior Member

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    I wasn't sure if Honda split the Sedan and Coupe ones, but it makes sense that they would.
     
  12. xbbnx

    xbbnx Senior Member

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    #117 xbbnx, Dec 29, 2019
    Last edited: Dec 29, 2019
    The Sport Sedan/Coupe do not recommend premium and are only required to use 87/regular gas. The only "Sport" designated Civic that recommends premium are the Sport Hatches. And also there is no such thing as a Sport Touring Coupe/Sedan, its just the Sport.
     
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  13. REBELXSi

    REBELXSi SeƱor Member

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    8 pages on this topic :rofl:
     
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