In reviewing my spreadsheet which has all the information on every fillup I've done along with other parameters, I have come to the conclusion that my recent experience with increased FE is partially due to break-in for the car. After 7,000 miles, I have seen at least a 2MPG increase in my FE.

Some may say that's due to warmer temperatures. That plays a part; however, I looked at my FE when I was driving under similar conditions of temperature and %Highway, and I still see that 2 MPG increase. Some of it is due to the engine, some due to the tires, some due to better understanding on how to drive. But I still feel that break-in is also a factor.