some of my suggestions.
Increase tire pressure, DO NOT go over the pressure listed on the sidewall. Increasing tire pressure will reduce rolling resistance but will make the ride less smooth, personally I did not notice much of a difference. My tire pressure is currently 40psi front and 41 in back. Once your engine has broken in sufficiently, between 5 and 10k miles, start using synthetic engine oil, Mobil 1, RedLIne, or Amsoil are good products that come to mind. Keep highway speeds normal if not slow. I don't drive like a grandma, but I usually keep the cruise at about 70mph. I was averaging almost 18mpg with only a 100 miles on the truck, I expect this to be my range on the highway and around 15 in town. Accelerate slowly from the light. This all sounds boring, but if you want to increase mileage these are some known suggestions that do in fact work. Now before you guys start calling me some kind of granny driver I will be more than happy to introduce you to the tail-lights of my 04 M3. Oh yeah, going from regular oil to synthetic, has, in the past, netted between 1.5 and 2mpg on different vehicles. I had a 93 F-150 extra cab long bed that never got 15mpg even down hill. After changing to synthetic tranny fluid, rear end, and engine oil, I would regularly get 16mpg, up from about 12 or 13.
Kind Regards,
Bryan