I'm actually closing in on it. 2 tanks ago I found my gauge calibration was optimistic (by I think 6-8%?) which was disappointing. However, I changed my oil from 0w30 to 0w20 and filled up with ethanol-free premium, compared with my typical E10, and this morning I peaked around 69mpg at one point in my commute. Given that there's traffic at either end of it, I don't think my commute is where I'll see 70, but I now believe it's possible. I'll check my tire pressure tonight and wax the car.
Surprisingly, I found I had to adjust my fuel trims by a full 5%, even though my math tells me E10 should only be ~3.3% different. It's possible we have more than 10% ethanol in our fuel here.