You can usually get better MPG without cruise control. Cruise control cannot adjust to things such as hills.
Good practices to increase MPG:
1. Coast to red lights, traffic lights, or slowed traffic.
2. Accelerate downhill (but not too hard).
3. Decelerate (a little bit) or maintain current speed when going uphill.
4. Try to maintain speed on the highway.
5. Avoid changing lanes too much (this causes you to speed up or slow down without you realizing it sometimes).
6. You can practice drafting on the highway but make sure you do it safely. (No, drafting is not the same thing as tailing...)
7. Windows up on the highway!
8. No A/C.
9. Accelerate smoothly to your cruising speed.
There are other things such as weight reduction and what not but I just want everyone to understand how to change their driving habits in order to achieve more miles per gallon.