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      12-30-2012, 12:25 AM   #58
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Drives: X1 x28i; 128i; S2000
Join Date: Jul 2010
Location: Orange County, CA


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I'm fairly certain that BMWs since the N54 are adaptive and will advance timing on higher octanes (93+) and environmental factors). I know there will be performance gains, not sure about gas mileage impact.

I just read that ethanol is often used to increase octane so that 91/92/93 gas may have more ethanol than 89 and perhaps lower mileage will result.