All my cars do run fine to 50% without CEL, the run fine even higher just get CEL for Long Term Fuel Trim for getting into the 20's and the car thinks something is wrong but they aren't running lean.
Wife filed the 2015 rogue with E85 (habit previous 2 car were FFV) I noticed it didn't start instantly as normal the next morning, later saw the CEL and figured out what she did. MPG dropped to 24ish, till I burned most of it up that day and kept topping off with regular.
http://www.speedperf6rmanc3.com/cont...evel_Study.pdf