Is it better to use cruise control or not for better mpg?

Using CC always seems to excede what I can do manually. I just walked in the door from an 80+ mile round trip that was all highway. I drove at 62mph, as much as possible, on the posted 55-70mph trip all with CC. I averaged right at 56mpg on the way there and almost 63mpg on way home. And the first leg was in Atlanta rush hour, bumper to bumper traffic sometimes going as slowly as 30-35mph. I have only beaten it once driving manually. That was a 5 hour trip, I beat it by 2mpg on the first part and my leg was killing me when I arrived. Since the Prius seems to be optimized for commuter type driving, anything gained on the highway, without CC, is purely academic. Also, given that the wind and road noise all but drowns out my stock stereo system, I consider mine to be an "around town and get me to and from work cheap" car. Another reason I feel this way is that the state of Georgia thinks the same. You can no longer drive alone in the HOV (high occupancy vehicle) lane here since hybrids tend to get better city mileage than highway.

 

Why, it's electric? I've not noticed that huge a difference in mpg's while using my AC. Your variable pot is the thermostat control. Another pot would be redundant. Carbon wiper pots for that would have to be gotten somewhere else other than Radio Shak or Fryes (three letters to remember when buying pots, CTS). Worst case, just bump the temp up with your thumb on the steering wheel at idle.

 

Thanks Strat, this car is Gen 1, belt driven. I basically want to delay AC compressor cut-in when accelerating and climbing hills, and extend the run time of the compressor when I am descending hills or decelerating- when I have excess"free" kinetic energy available.
I would accept the wider swing in cabin temperature, with the same average cabin temperature. The purpose of the pot would be to adjust the width of this swing, as an anticipator on a domestic HVAC thermostat does.
Further improvement could be bootstrapping the AC to GPS with terrain awareness....the car would see hills ahead and cool the cabin a few degrees more before climbing a hill.
I have Prius Envy of you guys with the more modern cars and their higher MPG!

 

Excuse my ignorance in not asking what gen you had. Forgot some were belt driven.

 

my experience over 50,000 miles and +4 years using a 2010 Toyota Prius III has been
wrt to getting the best fuel efficiency at a particular speed in all weather conditions...

on a flat superhighway speed road - driving with cruise control set - u can get pretty good fuel efficiency.

on a hilly superhighway speed road - the hypermiling technique called driving with load ( assisted gravity acceleration and deaccelation aka sling shot effect) produces the best fuel efficiency when assisted with Scangauge II xgauges LOD-n-GPH to measure the throttle.

other factors contribute to the Prius' overall fuel efficiency too...

Lower top speeds (under 60 mph) help increase fuel efficiency
Good weather and no traffic help increase fuel efficiency
Increasing you tire pressure helps increase fuel efficiency (+5 psi to 10 psi more or driving with LRR tires)
Driving longer than 45 minutes per trip increases your fuel efficiency
MPG does take a slight hit from having the AC on but not as much as speeding.

if one is stuck in bumper to bumper traffic jam in a prius - to get the
best fuel efficiency do mini pulse and glides - keeping your overall top
speed under 25 to 10 mph. (for third gen Prius u might also want to
switch to PWR throttle mode)

overall I'm getting about 60 mpg per year ... slightly more in the summer-late fall and slightly less late fall-winter.