You can run up to 30% E85 and not fear a code, it'll skew your LTFT's around 10% positive and is 94.5 octane.(E10 91 and E85 mixed 3:1) Positive fuel trims are carried over into the PE, just drive 5 miles or so until it adjusts before whoopin' on it.
I.E. 12 gals of E10 + 4 gals of E85 ~= 29% E
http://www.intercepteft.com/calc.html