I got a check engine light right at the end of the last tank. It went away, and relit shortly after I started driving on this tank, and then went off.
gallons E85: 4.011 @ $1.799/ gallon
gallons 87 octane gas: 9.449 @ $1.899/ gallon
ethanol content of tank: 32.38%
octane of tank: 92.122
Saving per tank compared to premium @ $2.399/ gallon: $6.182