Has the EV Button Boosted my Mileage?

I have always been skeptical of those who present the results of one tank or one trip and act as though it's fact or is even repeatable. So imagine my surprise when I started writing this thread.

When I got gas Friday afternoon, I did everything just like I always do: when I got my receipt I marked the miles on the tank, the MPG according to the MFD, and the total ODO on the car (to confirm the tripA). I was busy Friday night and Saturday was the Milwaukee Hybrid Group meetup so I didn't get around to entering the info into my spreadsheet until Saturday night.

I always enter the car data first because I have it right in front of me. Then I go online (dial-up) and get the weather information. To my absolute confusion, the average temperature had dropped while my per-tank MPG had increased. This if the very first time something like this has ever happened. There have been non-liner tanks before but always with me having lower MPG than expected usually due to low tire pressure or just stupid driving. I have no explanation for this one.

Except. . .
This is the first complete tank using the EV button. (Evan just blew chunks)
Like I said at the beginning, I am not proposing that this is true, scientifically accurate or repeatable. However, after checking the numbers and rechecking the numbers, I can not believe that driving style alone can be responsible for this because I was not intentinally doing anything differently than normal. It's not that I held the same mileage while temp dropped or even that my rate of decrease was not as dramatic as temp drop. I increased 1.4 MPG while the temperature dropped 5ºF. Looking at the chart availble through my signature, you can see how uncharacteristic that is.

It's going to take me a good three weeks to go through this tank. The whole time I will use my EV button in the same manner as I did through the last tank. Human nature being a variable of course. Don't get me wrong: I still believe that the EV button is not designed to increase mileage. But I have always hoped that in the right conditions with judicious and reserved use , we just might be able to use it to increase mileage.