My lowest tank ever was 11.8 and I was pretty mean to that tank. I think that's where half my tire wear went. Best ever was 20.4 on a trip actually doing the speed limit because of 4th of July weekend
speed traps. Average on road trips is normally around 18 if I keep it under 80 and my normal commute is about 75% city 25% highway and that averages about 12.6 regularly(+-.05mpg)