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So my 2013 Infiniti G37 requires premium gas (91 octane) but I just got it so I didn’t know, and I accidentally put regular gas (87 octane) into the car.

I filled my tank almost fully with regular gas. I have only done this once since I just got it, and I plan on using premium gas in the future.

I am not an expert in cars, but I am worried that my car might be permanently damaged from this. Is this true or do I not have to worry if I only do this once?

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  • What keeps you from siphoning it out? Jul 8, 2023 at 12:02
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    Where is this where 87 is still sold. Around here there are no options for anything lower than 95 Jul 8, 2023 at 20:35
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    @akostadinov I was surprised about this when I moved here too, but it seems like the numbers used in North America (Canada and the US) use a slightly different system: en.wikipedia.org/wiki/… so that “regular” here is called 87 and equivalent to something like 92 in Europe (still somewhat low compared to the now-standard 95 in many European countries, though).
    – Socob
    Jul 9, 2023 at 18:06

2 Answers 2

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It isn't going to matter in the long run and shouldn't cause you any issues to run the car with the tank of fuel you put in if that's what you decide to do.

Cars don't have an octane sensor. What they have is a knock sensor. When octane is too low (or for other reasons) and things go bump in the night (ping or knock), the knock sensor picks this up and pulls ignition timing to make the ignition cycle occur later in the revolution. This has the unfortunate side effect of reducing power. The car pulls timing so the low octane fuel won't damage the engine. As long as you don't push your car (think easy driving), it shouldn't have an issue.

Luckily, there is a way to fix your issue without having to drive it very much. There are octane booster additives which you can use right away which will solve your issue. Drop in a can/bottle and you should be good to go with no worries.

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    It could be argued that an "octane sensor" is a knock sensor, since the definition of the octane number doesn't actually have anything to do with octane in the fuel but only what isooctane-heptane mixture has the same knock susceptibility as that fuel. Jul 7, 2023 at 14:41
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    @Pᴀᴜʟsᴛᴇʀ2 the octane rating has nothing to with octane, either. Jul 7, 2023 at 18:54
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    @Kyle - Well that's Quora for you. Like I said, if you follow the directions, you'll have no issues. For instance, a 12 oz bottle of 104+ Octane Booster will treat up to 18 gallons of gas. I don't know if it will boost the entire tank up to 104 octane, but it should by all means get it above your magical 91 number without an issue. Mind you, this is not a cost effective way to increase your octane rating if you were wanting to substitute this for premium fuel. In your case where it is a one and done, it should work just fine. Jul 7, 2023 at 19:04
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    @Pᴀᴜʟsᴛᴇʀ2 well, no! Octane rating is a measure of how easily fuel knocks. Full stop. How much octane the fuel actually contains is almost completely independent of that. "Octane booster" is a nice evidence for that, because obviously adding a few ounces of booster to some gallons of fuel does not magically turn it into 104% octane. Jul 7, 2023 at 20:55
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    @Pᴀᴜʟsᴛᴇʀ2 Octane is not the fuel, at least not one anyone would actually use. Octane is one specific alkane that is a component of the fuel. Gasoline is a complicated mixture of dozens upon dozens of different organic compounds, including isooctane but also countless others. The octane rating is a specific comparison of the fuel's knock susceptibility compared to a standardized fuel of pure isooctane (which is fairly knock-free) or a standard mixture of isooctane and n-heptane (which gets more susceptible to knocking as the heptane proportion increases).
    – Hearth
    Jul 8, 2023 at 15:08
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I had a G35. I believe there was language in the owner's manual that said regular gas would not hurt the engine but you would not get full performance.

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