New owner, disappointed in mpg...

...ethanol lowers mpg 1-2 mpg, so skip it if possible. But you are reporting an unusual fuel choices. Normally if you live in zone that requires ethanol it is in all grades. Normal Regular is 87 octane (R+M/2) but high altitude zones may have 85 instead and that is good.

 

...I believe you are indeed good with 85 but let's hear from mile-high-club. Sea level here.

 

You could possibly benefit from running 91 vs. 85. If you have a lot of hills, then running 91 will keep the ignition from retarding as much under the load, making it more efficient. Usually the effect is marginal, making the slightly increased MPG not good enough to offset the higher cost of the fuel. On a very high mileage motor, carbon buildup causes compression ratio to increase and high octane fuel can help improve MPG there as well, for the same reason. It won't hurt anything to experiment, although there is a very slight chance that the 91 octane will lead to hard starting in very cold weather. There is an admonishment in the service manual about high octane leading to starting problems, but IMHO it is directed at 94+ usage in Canada.

 

On my 2010, higher octane fuel reduced my mileage.

 

Go to pure-gas.org for the 5000 gas station addresses & excellent zoomable map, selling 100% ethanol free gasoline & the few sellers in S. Dakota. Possibly you can find another station that gives you better options for octane ratings. As for me, switching to 100% pure gas raised the mpg of our 3 cars by 8%, 7-8%, & 6% & those figures were obtained including the winter. All 3 engines are smoother, quieter & need less downshifting when ascending hills.