[KingWarren2]

I'll get straight to the details pretty much, 99.5% of my driving is highway driving, I live off a highway, my work is off a highway which is 2 hours from my house.

Speed limits are 60km/h, 80km/h and 110km/h.

What I've noticed is,
Cruize P) control at 60km/h jumps between 4.9l/100km and 12.0l/100km
At 80km/h jumps between 3.6l/100km and 8.6l/100km
at 110km/h jumps between 3.2l/100km and 6.8l/100

However, and this is easy for me as I've just upgraded from a car with and pedal controlled throttle body, that if I drive the car all on my lonesome without any cruise control, in gear 5 I can sit comfortably at 2.9L/100km while keep speed, which is actually huge considering you're not spiking and demanding more fuel for little inclines etc...

I'm assuming GM has a rather sensitive throttle?

This was on a turbo diesel 2010 2.0L holden cruze by the way, 35L out of the 60L tank has gotten me 777.5km and that was using all cruise control, I think I could see an increase of atleast 35% doing manual throttle control.

 

[chevrasaki]

You'll usually get better economy driving with your own foot because you can adjust your speed a little. Accelerate on downhill and maintain speed without accelerating or decelerate slightly on uphill portions. Hyper-miling is pretty stressful so I quit awhile ago.

 

[grs1961]

That's interesting, mine doesn't jump around anywhere near that much, but I don't rally watch it that closely.

I find it difficult to keep my foot light enough at 100km/h to keep it as low as 2.9l/100km, anyway

I might watch what it does, but too much of my driving is in traffic to really take my eyes off the road and focus on the instant value, old eyes take time to re-focus.

IOW - I turn on cruise, and watch for idiots.

 

[obermd]

I find cruise control gives better overall long term efficiency results.

 

[Pegasus]

You'll usually get better economy driving with your own foot because you can adjust your speed a little. Accelerate on downhill and maintain speed without accelerating or decelerate slightly on uphill portions. Hyper-miling is pretty stressful so I quit awhile ago.

I've noticed this with other cars in general as well, particularly if the highway is very hilly. The wife and I have found though that the main reason for cruise control isn't so much MPG but avoiding accidentally going way over the posted speed limit. When in the cruze, it doesn't appear visually to us to be going as fast as the speedo indicates. We've comfirmed it however with a GPS, the speedo on her new cruze is spot on in all speed ranges.

 

[Pegasus]

My wife was halfway through a test of the mostly city driving MPG in L6 mode in a 2017 gas LT cruze, when she had to use it to go do about 160 miles of straight highway and interstate driving, which would've thrown off the results in comparing it to almost all city in D mode. She did the highway driving in D mode. So since we have to start over anyway, here are the results of half city, half highway. 338 miles / 9.28 gal = 36.42 mpg She didn't drive like a little old lady on sunday either. It's not the almost 43 she got the 1st highway trip, but that was all highway, not 50/50, so I guess that's okay mpg.

Oh, b.t.w., I mentioned in another post about how when we first took the car home from the dealer we had problems, like it was sputtering going up a steep hill. We haven't had any more issues yet, so far runs like a champ. (but it is still low mileage not broke in yet)