As I mentioned before, I travel the same couple miles everyday and it bores me so much that I look at my mpg needle on the dash... if you're accelerating to something like 45mph on a local road and want to stay there, typically you'd keep your foot on the gas just enough. What you actually can do is let off a tad and the needle will show that your mpg increases quite a bit... if you hit the gas again just a bit to maintain, it will still show better mpg. I'd say at least by 10mpg on the meter. I don't know if it messes with the gearing but you're basically going from a pull to a coast. Seems like common sense but we drive in the 40mph range so often on local roads that you just don't think about stuff like this. I just find it interesting how much you could possibly save if you wanted. Personally, I don't drive frequently enough to care... I spend about $120/mo. on gas, 2 fill-ups.

__________________
'08 X5 3.0si - Alpine White / Saddle Brown interior
Specs: Sport Pkg, Premium Pkg, Tech Pkg, Comfort Access, Aero Kit, Style 433 staggered 20s on Conti DWS
Mods: Carbon 35 tint, LED angel eyes, GP Thunder 7500k fogs, H&R 20mm/25mm spacers, clear reflectors, gunsmoke-tinted taillights
Coded: Digital speedo, windows/sunroof/tailgate close via keyfob

X5 pics at Flickr