If MPG is a big concern for you then you have purchased the wrong car.
Let's face it, if there's a 1-2MPG difference, you're hardly going to feel it at the pump every Sunday.
However, if it was a 10MPG difference, believe me, you'd already know about it.
And based on that - I wouldn't concern yourself.
If you're that worried about MPG, I hope you never use the air con, never have the windows open, never listen to the radio, always have your tyres at the correct pressure and you're are at your recommended body weight for your height (or less).