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      04-28-2014, 07:15 PM   #2
jadnashuanh
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Drives: 535iGT x-drive; i3 BEV
Join Date: May 2010
Location: USA

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The computer will adjust the timing and operating parameters to adjust the engine operation to the conditions and the quality of the fuel. But, there are limits. When the octane is below the range it can handle, it could cause engine damage. You are only guaranteed the design performance if it has the desired octane. When the computer detunes the engine, you will get less MPG and performance, so in the end, it may end up costing about the same or even more to use the lower octane since you'll use more of it. Driving very conservatively, you may not notice the performance differences, but most people do notice.
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