Cummins did some experimenting on making a medium duty E85 engine. Pretty good read.
Cummins 2.8L E85 ETHOS Project
Can't find the full text of the study seems to have been removed from the web, it had technical specs on the full development.
Found reference to a 2005 study using E30 by the EPA with 1.9 liter engine with 17.5ish compression that got higher FE than E0 but haven't been able to find it.