I just finished my first tank on my new '06 civic - I got 49.1mpg over 550 miles - I was very impressed.

However, yesterday before work I filled up and did the exact same commute and I got 59.1 mpg!!! Can anyone tell me why the difference?

I had my cruise control set to the same as I had on the first tank - 63mph - and I drove in the same traffic which I fight every day - I commute 50 miles one way to work. It was a little warmer out - probably 8 degrees warmer - would this make a big difference?

Why would I get 10 more miles to the gallon? Is the car breaking in? I have over 550 miles on it now.

Your feedback would be appreciated...thanks!