Angela, I'm pretty sure you'll notice 3 pounds difference in several ways. Let us know.

On the tangent topic of cruise control, CC will probably appear to be giving you better MPG as long as the road is straight and flat. Where it fails is when you introduce hills. CC wants to maintain speed above all else, that's its mission in life. So, when you start up a hill and speed starts to decline, CC punches the throttle as hard as necessary to maintain speed. Now, you, as a mpg-concious hypermiler, will see the hill before you get there and maybe breathe on the throttle just a little more to gain 5 mph before you get to the hill... and then allow the car to lose 5-10 mph on the way up the hill, and then on the downhill side, you'll gently regain your speed and then some... all while using less fuel than your CC would have.