Compared to what? It depends on terrain and driving still. On long flat stretches at freeway speeds, it is probably hard to beat. At slow speeds you can probably beat it with pulse and glide technique. If you generally pay little attention to driving technique for efficiency, CC will probably do better. As terrain gets hillier, you will be able to beat it if you have some way of monitoring engine load (your instantaneous MPG will do if you have nothing else. Cruise control is overaggressive on hills. Remember, it is quite stupid, and will try to maintain the set speed at all costs, hence a reduction in fuel efficiency, esp. on varied terrain.
i use CC most of the time, my SO does not... not counting other obvious differences between us, it is equating to a 5 mpg drop in mileage. i use CC on streets where speed limit is 30 mph or higher and yes in town, its a lot of engage-disengage going on, but i still believe that it gets me better mileage then controlling speed manually simply because i am unwilling to devote the attention necessary to get better mileage.
With my own observation and with our semi-hilly terrain interstate, I noticed that I get less mpg when I use my cruise more often. The last tank I had I've used cruise of and on...I dropped from 46 mpg to 42.85 mpg. As mentioned earlier, I'll only use cruise control on a nice flat highway/road. Drive safe.
When we lived in flat South Florida, cruise control helped our FE. Now we live in hilly Tennessee and cruise control hurts our FE.
I get better without the CC. But, on long trips (over 250 miles or so) I use it anyway to keep from getting so tired.
Willie is pretty much spot-on, from my experience. First, for highway use, see this writeup on a comparison of CC vs. manual pedal control. Second, at 40 MPH and below, pulse and glide seems to provide favorable results as indicated by experience, some preliminary testing, and numerous anecdotal reports. I've not completed testing on that, however; that's a project for warmer weather.
I used to run with it all the time on highway driving but gave it up. saw mileage improvement. however, I have recently started using it again on highways on long uphill climbs, clicking off just before the crest. it's pretty hard to p&g up a long steep hill.......
Just recently finished the inaugural drive from Downeast Maine to Dayton Ohio through Penn. The cruise is not so good in the mountains or hills, in my opinion. I did better on the mileage by myself. Cruise is stupid; without some sort of radar system it does not recognize inclines coming up, oddly enough. I can see them coming and can compensate. As a side note, our first real drive with the Prius and we avg. right at 46 to 48 mpg.I was impressed with the car. Especially the $14 fill-ups.
For long duration, steady speed travel the cruise control will return the best mileage returns, because it is more precise at maintaining speed and maximizing electric only operation, when driven at a moderate speed. And speed is one of the biggest keys to great gas mileage. 60 MPH = 60 MPG on the highway. Speed much over that drastically reduce gas mileage. Back-road, sideroad, driving...turn off the cruise and train that right foot to be light and precise. Learn how to glide and warp stealth.
