Well, as of right now, I’ve seen a swing of about 12-13 percent (E68ish at exit 23 in Mid April, and E81ish at the Airport Mobil last week). I’d venture to guess that your tune in March was on E70(ish). But if you’re car is truly in closed loop all the time, it should be making corrections for ethanol content ‘on the fly’. Regardless, from what I’ve seen so far, I don’t think your car would be dangerously lean on E80 if it was tuned on E68-70…given the fact that I saw NO change in AFR’s when going from E81 to E76. If there is NO change with a 5 percent swing, how much will there be with 10?
You gotta realize how LITTLE gasoline it takes to change ethanol percentage. For example, to turn 10 gallons of E80 into E70, you’d only have to add 1.25 gallons of pump gas (to the 10 gallons of E80).
BTW, I really want to check out your car sometime. PM me with what it made at the wheels…