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Thread: Can I use 89 Octane rather than 91 Octane as my OEM suggests using?

  1. #1
    Senior Member
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    Nov 2008
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    Can I use 89 Octane rather than 91 Octane as my OEM suggests using?

    I have a late model BMW and with gas prices ballooning, I would like to use 89 Octane rather than 91. Would I be hurting the motor?
    Just curious guys.

  2. #2

    Re: Can I use 89 Octane rather than 91 Octane as my OEM suggests using?

    The short answer is Yes, though whats the point as you wont get the performance that the car was intended out of it. Your ECM will compensate so as not to detonate which will result in a loss of power, fine if you keep your foot off the gas plus your overall fuel mileage may go down. So park it and get an old VW or pay the Obama tax!

  3. #3
    Senior Member nicktruman's Avatar
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    Re: Can I use 89 Octane rather than 91 Octane as my OEM suggests using?

    I tried running 89 in my 325i, for a week or 2 all seemed OK, then the car started acting wierd and kangarooing. Never again, it felt like i was driving a bad diesel with half the cylinders missing!

    when I am in the UK i use Shell V power in my ferrari. The cars runs so much better.
    Regards
    Nick

    Twin turbo V8 Zonda inspired thingy

  4. #4

    Re: Can I use 89 Octane rather than 91 Octane as my OEM suggests using?

    I was running low on gas and pulled into a small town where I pumped in 87 octane gas into my 540i and didnt think I was going to make it home. I stopped in a larger town and bought some octane boost and when the gas tank was half full I topped it off with 91. Check engine light came on with the 87 octane Caseys gas. I wouldnt do it again.

  5. #5

    Re: Can I use 89 Octane rather than 91 Octane as my OEM suggests using?

    With the modern knock sensors now days, the car will run, but not well. I would never use lower or higher gas than the manufacture recommends. With lower octane, the engine will want to knock. If you knock the engine enough it will fail. The real question is how much money are you saving by risking your engine. The difference between 89 and 91 is usually less than 10cents. Your BMW has a tank smaller than 20 gallons, but lets think about a 20 gallon fill up with a 10 cent cost is $2 more. You are willing to risk destroying your engine for $2. Time to get a Civic my friend.

  6. #6

    Re: Can I use 89 Octane rather than 91 Octane as my OEM suggests using?

    I got a bimmer too.. (not to be mistook for "cheap") However, I don't think that there is a more frugal, cost conscience, fiscally conservative person on this site other than I. With that being said.. I would never ever never put cheap gas in my car..

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