Is Bio Ethanol Gas bad for your vehicle?

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BMW say anything at the recommended octane is fine, including Husky 10% ethanol fuels. Anything below 92 will be fine once in a while when premium is unavailable.

The consensus on the BMW forums is that anything detrimental will be in the long term & wont show up until after the car is out of warranty. Therefore BMW may say it's fine because nothing will show up in the warranty period & they won't upset any of their oil partners/suppliers by telling customers not to use some of their fuels.

Porsche say the same thing but advise that performance & economy will be reduced by roughly 5% on ethanol fuels.

I just want to know the long term effects of ethanol fuels on engines that need to 'compensate' for ethanol rather than engines designed to run it.

Which Chevron has the 94? The one by Wendy's/Walmart didn't seem to have it.