From your link:
The RFA, of course, highlighted the NREL’s finding that there were no “meaningful differences” in the performance of engines running on a 10-percent ethanol blend (i.e. E10, which is standard-issue in the US) and a 15-percent blend (i.e. E15). Using 43 studies as a base, the NREL surmised that, when it came to engine performance and durability in light-duty vehicles that were made after the 2000 model year, E10 and E15 are basically the same thing.