If you tune rich for e70 in the winter (like .4 richer than normal), it would be fine for e85. You just cant push it to the very edge like you can with race fuel. We only get about one or two months of true 85% up here, most of the time its 70 or 78. Flex fuel cars have trouble starting in the winter on e85, thats why they lower the amount of ethanol in the winter.
Here is the chart of what gets shipped when:
http://www.jeffgst.com/e85global.html
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