Chris the only time I start out in second is when the streets are slick. It works much better than first. Other than that I agree with Mike that on a dry road you are putting extra stress on the drivetrain. I always try and get it in 6th as soon as I can. With the lower revs I would think that is where your fuel savings would be. My experience with manual vs. auto is that the manual always gets a little better mileage than an automatic and remember a lot of it is how you drive the car. Someone who drives agressively is obviously gonna use more gas than someone who is light on the gas pedal.
Be Safe!