So what truly constitutes a 'bad tank' of gas? There have been times when I've documented every fill up, mileage etc. religiously and there were variances but nothing earth shattering and none of the different brands really seemed to run better. I found the most difference in what my commute was during the week and at the time I was burning through about 1.25+ tanks of gas per week, not so much now though.
My Focus averaged 35+ MPG on a December trip to Mammoth including around town driving; I though that was quite good indeed for a car rated at 30MPG. (My normal mix of town / freeway driving is ~30MPG.) I'm pretty sure I bought the Gas for the return trip at Ft. Independence as well.
I really do sometimes watch grass grow, just for fun. Could be due to spending all summer getting ready to finally plant grass..