Help me with my commute

I decided to make this week a "control," and to drive normally. After two weeks of attempting to hypermile, it was difficult not to P&G, but so far I haven't. However, I still coast if I'm going downhill or if I see a red light, which is what I used to do in my non-hybrid Kia Optima.

I have actually gotten an increase in gas mileage. Today, driving normally and using cruise control, I got 56 mpg.

The only conscious difference is not hypermiling. I don't think my technique was so bad as to actually cause a decrease in mileage, so I'm wondering if fuel quality could count for the difference. This tank is from a top-tier brand while the last tank came from Sam's Club.