I searched and found several threads going back many years debating the merits and issues of using ethanol blend fuel in motorcycles
but I did not find any where riders tested their own bikes and reported their measured results and data.
Reading in some recent threads tracking Vstar bikes fuel efficiency there were comments being tossed about on 10% ethanol (E10) causing a significant reduction in mpg performance, engine performance, and whether regular vs hi octane fuel offers any difference if your bike does not require hi octane fuel.
This sparked my curiosity and I decided to test my 2005 Vstar 650. I have been running E10 (as far as I know) since I got the bike 5 years and 30,000 miles ago. Its fully stock and typically gets 58 or 59mpg when I check it. On a few longer trips at 50 to 60mph it has bumped up to 61 to 63mpg, but that has been difficult to duplicate.
So... last week I found two gas stations in my entire county that have 87 octane ethanol free gas, using this website: https://www.pure-gas.org/index.jsp?stateprov=NY
there are many that have 91 or 92 ethanol free, but only two that sell 87 "E0".
Filled the bike up with the good stuff last monday, the mileage on the trip odo and the fillup registered 58.5 mpg for the previous tank of E10 fuel. It cost $3.50 per gallon and E10 in my area is selling for $3.00 this week. So it costs 17% more to get 10% more gasoline and no ethanol. I dont understand that at all!
Guess I should mention that GPS shows my speedo is accurate to within 1 mph - but since I was looking for percent change, not absolute mpg performance, that is not an issue.
I will try to keep subjective information to a minimum, since it cannot be measured or documented. To me it seemed like the bike was running better on the pure gas. The motor seemed to run smoother when acceleration and shifting up, it seems like its popping and snapping less when fully compression braking at the lower engine rpm. It seems like the fuel/air mixture has been slightly increase to the richer side, which is what you would expect if gasoline has more energy per gallon than ethanol.
After a week I pulled into the same station with 245 miles on the trip odo (a new record for me) and it took 4.19 gallons of gas to fill the tank up click click click to where it stopped settling back down the filler tube in the tank.
That is 58.5 mpg. Exactly the same as the E10. That was disappointing.
Also interesting to note the tank on the 650 is 4.2 gallons, so I had 0.01 gallons of gas left in the tank when I pulled up to the pump. Thats 1.3 ounces, less than 2 tablespoons. I got lucky!
Since my bike has carbs I dont expect the engine to tune or change to the ethanol free gas like a car with fuel injection and a fully closed mixture adjustment loop on the O2 sensor.
I will track my mpgs on this 2nd tank, but I have no reason to expect it to be any different than the first.
Im not really interested in hearing antsy-dote stories about the evils or merits of putting ethanol in fuel - there are plenty of threads on that going back 6 years or more, and its all been beaten to death. If you test your bike on ethanol blend and free gas then post your results.
I think I might also try running the bike on premium gas (ethanol free) since it is more widely available, and see if that has any effect. Since my bike has carbs I expect I might get lower mpgs on hi octane, because the bike as no ability to adjust the fuel / air mixture, or to change the spark timing to take advantage of the higher octane fuel.