You should be fine because the content of ethanol vs the 93. From the start you are putting 3 gallons of e85 and 9 gallons of 93. Of course the safe answer is going to be to run the tank as much as you can go. The bigger thing would be that if you are running an aux fuel system to do some low boost pulls to clear out what ever is in the aux fuel lines out. With ethanol you are able to lean the car out more than on 93 so if you are monitoring your ignition corrections, knock count, and afr and everything is looking good then you are golden. Hope this helps.