Here’s a little test I did to bolster the argument for an actual ethanol sensor (non-virtual) if you’re going to run it as your usual fuel.
I personally haven’t ran it for a few months, but since I have an ethanol sensor, I figured I’d show folks what the actual ethanol readings would be.
I started with 1/4 tank of E11, which is accurate given that pumps in my area are ~10% ethanol.
I added exactly 6 gallons of E85. My local refill station measures at exactly E85. YMMV, but I recommend testing the ethanol level at your station as seasons change as the blend may change. Mine is pretty consistent at ~E83 - E85 year around.
After adding the ethanol, which brought me up to about 3/4 full on the fuel gauge, I filled the remainder with 93.
After letting it mix over several moles, you can see the resulting mix is E35 with a target of E30.
This isn’t a huge difference, and as Terry mentioned the ECU should adapt accordingly. However, if you’re trusting the virtual sensor with +/- 10 point accuracy, you can quickly see where things become an issue especially if yours reads low and you decide to add more E85.
Lastly, for those who intend to run E30 all the time, if you’re already at E35 and you refill 6 gallons of E85 and top off the rear with pump gas, you will continue to increase the ethanol content each refill. Remember the base was E11. You’d be starting with a base of about E35. To prevent having too much ethanol, you’d need to run your tank dry before each refill.
