I decided to do a little test to see how much more (if any) gas my car was eating with cruise control on vs using my foot to control speed. Wow was I shocked at the results. This is the same stretch of road and I reset the computer after I had already reached highway speed:

Cruise Control ON:
Distance: 11mi
AVG Speed: 65mph
MPG: 19.8

Cruise Control OFF:
Distance 11mi
AVG Speed 64mph
MPG: 24.4

With 3 Passengers-
Cruise Control ON:
Distance 11mi
AVG Speed: 64mph
MPG: 19.8

Cruise Control OFF:
Distance 11mi
AVG Speed: 66mph
MPG: 23.9

So according to this rough test, my car gets about 20% better mpg without using the cruise control. I'm going to think twice before being lazy and turning it on.

 

i think if you were on a perfectly flat road the cruise would do a better job than a human. the problem with most cruise control's is that it does not allow the car to speed up going downhill. when in a manual you can usually just let go of the gas and carry your speed all the way down the hill without using any gas at all, or continue to use the same amount of gas and speed up.

 

I always noticed I got better MPG with my cruise control set versus my heavy foot.

 

^ hmmm. me to.

 

Hmm funny, in every car I drove, I've always gotten better MPG no matter where I drove. :shrugs:

 

i would think on average you probably would, I just wanted to point out that cruise will not always be the most efficient in certain (temporary) circumstances

 

hmmm i use my cruise only on the freeway, oo btw what car were you using to do your testing?

 

Were you going the same direction in all of these tests? Or was it one direction CC and the other by your feet?

 

Must've been the Mercedes because he took 3 passengers (it's in his sig too). I didn't think c.c. would have affected gas mileage that much.

 

Sounds like a computer issue to me. Cruise should be more efficient.