Running a MINI on regular-grade gas

Discussion in 'BMW' started by some_other_dave, Mar 11, 2014.

  1. some_other_dave

    some_other_dave Well-Known Member

    So, BMW says that my MINI requires at least 89 Octane, and recommends at least 91 Octane. (Both AKI, which is the scale used in the US, so no RON vs. MON vs. AKI confusion.)

    Due to a pretty massive brain-fart on my part, my last fill used regular unleaded, which in my area is 87 Octane.

    I detected no ill effects. There was no audible detonation (pinging), no check-engine lights, and my FE didn't appear to suffer at all. In fact, where I would have expected it to be lower due to some driving in fairly mountainous terrain, and due to pretty heavy rainfall recently, in fact my tank was almost 1 MPG better than my previous tank! (43.8 versus 42.9, I believe.)

    I'm not willing to repeat this experiment intentionally, at least not until the warranty runs out, but it is an interesting data point.

    Now, it is possible that the power output was down--but at the speeds I travel, that is a non-issue.

  2. RedylC94

    RedylC94 Well-Known Member

    What was the typical altitude of that "mountainous terrain"? High altitude might've helped.
  3. GrnHrnt

    GrnHrnt Well-Known Member

    My grandfather was a car enthusiast and owned all sorts of sports cars both American and German (Ford, BMW, Mercedes) although many of them called for higher octane gas he always put regular in them.
  4. ALS

    ALS Super Moderator Staff Member

    All that will happen will be the computer will retard the timing causing a drop in power at higher loads and a slight drop in fuel economy. If you drive like most of us here you won't see much change in normal driving but the fuel economy hit will get your attention.
  5. some_other_dave

    some_other_dave Well-Known Member

    The maximum altitude of the "mountainous terrain" was on the order of 1400 feet, not enough to make a real difference IMHO. And most of the driving was done at something more like 50 feet altitude.

    No MPG hit at all, and in fact slightly better than the previous tank. It's an interesting data point for you.

  6. roadrunner

    roadrunner Well-Known Member

    What have you been using in the 2012 MINI Cooper?
    My wife has been using 89 in her 2010, and it has been running great since new. She never tried 87 or 91.
  7. some_other_dave

    some_other_dave Well-Known Member

    I've been running 91, apart from that tank. (All California's RFG.) And I don't know what was originally in the tank.

  8. jcp123

    jcp123 Caliente!

    Modern engines have knock sensors which prevent any ill effects of knocking. All you notice is maybe a loss of power and sometimes a loss in fuel economy. My SVT Focus suffered a lot when I used 87 instead of the recommended min. 91 octane (premium is 93 octane here), as much as 2mpg. And it had a 6-speed I short-shifted at around 1500-1700rpm.

    May be a bit of a different case was a hot hatch with a 7500 rpm redline and a Cosworth-engineered head on a 2.0l Zetec block, VVT on one cam, factory headers, 17" wheels, etc. designed to compete with the Civic SIs of the world. Never really intended for efficiency. In-town it was a hog and never yielded much more than 28mpg on my commute. I have learned a bit more now but don't feel I could have pushed it much past 30mpg. Out on the highway it was good for 36mpg with nothing but the constant TPS I practice today. Strange car. A nice one too, great ride vs. handling balance, nicely laid out inside. Hatchback versatility, I liked the extra gauges. Nice exhaust note for a 4-banger. Comfortable seats, very stable, quiet, made a great long-distance tourer. Shame its quality was more 80s Detroit than modern excellence.
    Last edited: May 24, 2014

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