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BMW Mini Cooper

 Fuel octane / engine damage

 Created by: JayA1010
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 Posted: Feb 2, 2020 06:54PM
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I've run my 1275cc FI mini since new on premium gas. 61K. Still running. It's all the rubber parts that fail, disintegrate or split apart.

 Posted: Jan 27, 2020 05:21AM
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The difference in price between a tank full of regular vs. premium doesn't even cover the cost of a starbucks drink....  I would go ahead and follow the manufacturers recommendations....

As Doug mentioned, 'if' the engine knocks because of regular gas and the computer pulls back the timing - it is not running under 'optimum performance'. 

Typically speaking, better performance = higher costs ....

 Posted: Jan 24, 2020 08:42AM
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Gotta wonder why people would think manufacturers would specify something like fuel octane if they didn't think it would maximize the performance & longevity parameters they designed into the car.

Higher the octane, the slower the burn/flash rate because the flame must burn the additives. Lower octane fuel actually burns faster.

Think of it like a merry-go-round at your elementary school playground. It's sitting at a dead stop. Now slap it and see how far it moves.

Ok, now that your hand is hurting, go ahead and grab it and give it a shove. How far does it move now?

As it is moving faster, there comes a point where the time you are in hand contact with the merry-go-round becomes less and less and, yeah, you need to start slapping it at the higher rpms.

The subtle changes your own brain makes to where and how hard to hit the merry-go-round with your hand are like what the ecu does to adjust timing.

Can you make the merry-go-round go...uhh... round just by slapping it from the get-go? Sure. Can you do some serious damage to your hand by sticking your hand in there at the wrong point or while moving at the wrong rate? Yup.

Anyway, I think I started to lose my point.

At an average of 28mpg over 10,000 mi per year (1,517.85gal annually) and if premium fuel is $.20/gal more than regular fuel, that's $2.64 per FULL tank of gas or $303.57 a year. If you order a glass of water instead of a fountain drink at most sit-down restaurants nowadays, it'll save you the same amount or more.

 Posted: Jan 24, 2020 06:58AM
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Since I do not own a MINI, please consider the following to be just some general information.

In general, the ignition timing is adjusted to work with the grade of fuel you are using.  On old cars this meant a mechanical fixed adjustment followed by a test drive to listen for knocking and pinging.  Being a modern car, the MINI almost certainly uses an electronic knock sensor to feed information to the ECU.  The ECU will adjust the timing "on the fly" to get the most out of your gas.

If you put regular in the MINI the ECU will probably retard the ignition timing a bit to maintain smooth running without knocks.  Running with slightly retarded timing will reduce the power output a bit and that in turn is likely to slightly reduce fuel economy.  It may change the emissions a bit also but the ECU will also be adjusting the fuel/air ratio to maintain an acceptable level.  

As for wear and tear, IF the ECU is able to retard the timing sufficiently to prevent knocking there will be no additional wear and tear.  If the ECU cannot compensate, there will be knocking and pinging and that will cause wear to components like the engine bearings.  

Someone versed in MINIs will know the specifics that I don't know.

Doug L.
 Posted: Jan 24, 2020 06:24AM
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My 2004 Cooper S recommends a premium octane rated fuel. I understand that the ECU, will allow the engine to run on "regular" gas. What would the engine performance, fuel economy, and longevity of all engine parts including the emission systems, be if only regular gas was used. I am trying to get the best "cost per mile". Thanks