I’m not sure, I never try to run anything higher than 14.99% as in NJ it can still be called Gasoline up to 14.99 %, anything over that % legally it’s supposed to be called gasohol. You can bet your dollar every company out there here in NJ is using the max amount of alchol allable in there fuels and have measured it to confirm many times. Never have I measured and came up with a lower %. But the fact is companies have diluted especially winter fuel as I can see the difference especially in colder month with my fuel milage when I had a gas engine, I have measure up to 47% alcohol and NEVER ran any gasohol ever? Go figure, seems like mostly winter months high concentrations as fewer drivability symptoms in colder weather with high concentrations in many cars/trucks. I use to test my fuel for the alcohol % about 4 times a year, before now, I own a diesel 3.0. I think your chart is very interesting and all I know is what I read and everything I have read till now states the BTU rating is about 40% lower. I also know I personally could see in one tank, full fuel milage drop with anything over 25% easy. I’m not sure who is cutting the fuel, station owner, distributer? But I know it happens and still see it happening when I take samples, but now it’s more of a learning lesson for the students I teach, to show them it does happen and often here in NJ.
That being said benifits, Higher octane creating a more controled burn and never have to worry about water freezing creating troubles. Hurts the dry gas market