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      01-13-2013, 01:28 PM   #42
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Drives: 08 E90 M3, 99 E36 M3 Turbo
Join Date: Feb 2011
Location: Concord, NH

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Originally Posted by MRSSIIM3 View Post
but 93 in the east coast is 10% ethanol whereas 91 in cali is 0% ethanol. So at the end of the day, they are pretty much equal

i could be / probably am completely wrong about this. thats just what i always thought lol
I think 93 octane is 93 octane even if it has 10% ethanol. Remember that ethanol is not necessarily bad. If you have 85% ethanol, your octane is much higher than if you have 85% gasoline. The problem is that it takes a lot more ethanol to make the same power so if you run E85, you may need larger injectors. Also the ideal AFR for ethanol is different from gasoline, so the tune should be adjusted. In the 10% range, I don't think it matters much. I'd rather run east coast 93 than west coast 91.