Adaptive Cruise vs Regular Cruise Control - Anyone See Difference in MPG

[DanSkan]

Has anyone noticed a difference in MPG efficiency with adaptive cruise control vs regular cruise control on? The adaptive cruise control is "hunting" for the steady set speed and adjusting for distance between vehicles ahead and the ECO light (MDS) doesn't seem to come on as often. I love the adaptive cruise control on my vehicles and am spoiled using it - it is hard going back to regular cruise control. I haven't driven enough highway miles/trips yet to determine the difference in MPG.

 

[U-235]

I can't imagine why there would be a difference. Road and traffic conditions being exactly the same, the truck would accelerate and decelerate the same way in either case, unless you mat the pedal every time someone moves out of your way.

 

[silverbullet]

I don't have the adaptive cruise but I have noticed that with the cruise set and without that I can get the same steady speed and keep MDS on longer/more often than cruise does for most situations so I could see there being a slight difference in the right situations. I'm learning the trick to MDS and throttle position over time so there's certainly some tricks to really get the most out of it.
IF I shut off the cruise when I'm approaching my turn and just let the truck coast it usually doesn't even get to MDS before I stop BUT if I'm in control and I ease up on the throttle I can make MDS enable and it remains until I coast to a stop.

I read the reason that the e-torque got a 1 MPG improvement on the HWY was the battery helped MDS stay active more often, the engineers weren't expecting it to matter on the EPA cycle but it netted 1MPG hwy nonetheless. Throttle position has a lot to do with the activation in my experience; moreso than any other factors from what I've noticed.

 

[Edwards]

I've got no hard data but after using the adaptive cruise on some long trips I would be shocked if it's getting the same MPG. You really have to retrain how you drive because if you cruise up on a slower vehicle, the adaptive will brake to match their speed. If you were driving, you might coast or just get closer. In any case, that braking has an effect on your MPG.
You also wind up with a lot more slowing/speeding up with adaptive due to other traffic. That loss of speed and subsequent speeding back up takes a hit as well. What the real difference is, I can't tell you but it's not zero.

 

[392DCGC]

Not sure if the acceleration profiles are different between ACC & regular cruise, but I doubt it. Regular cruise might not apply braking if you go over speed though (e.g. going down hill - ACC only lets you go +2 MPH before it begins braking). One thing I've noticed with this truck vs all my previous Mopar's with ACC is how aggressive it is to accelerate with ACC... not sure if that's by design for fuel economy (if accelerating at a healthy pace is more fuel efficient?), or if it's for customer satisfacton for people who typically accelerate quickly.

I've got no hard data but after using the adaptive cruise on some long trips I would be shocked if it's getting the same MPG. You really have to retrain how you drive because if you cruise up on a slower vehicle, the adaptive will brake to match their speed. If you were driving, you might coast or just get closer. In any case, that braking has an effect on your MPG.
You also wind up with a lot more slowing/speeding up with adaptive due to other traffic. That loss of speed and subsequent speeding back up takes a hit as well. What the real difference is, I can't tell you but it's not zero.

Eh, I disagree with this. Unless the vehicle in front of you is going dramatically slower, stopped, or suddenly merges into your lane, the adaptive cruise will pick them up far enough away to coast down to their speed without wasting fuel/braking to match it.

 

[SpeedyV]

Consider your use case. There aren't many situations where standard cruise has any advantage over adaptive cruise. If you're following another car at a more-or-less steady speed for a hundred miles, adaptive cruise wins hands-down. No need to manually adjust speed, disengage cruise, etc. This is the most economical state possible, as you are basically drafting them (at a safe and respectful distance, hopefully) with no manual intervention.

If you are working your way through heavy traffic, especially stop-and-go traffic, you may find adaptive cruise performance to be less than ideal—especially when some friendly driver cuts you off. The braking and acceleration behavior in close quarters may be a little more 'jerky' than you'd like. You'd be better off disabling cruise control entirely in that situation, as @Edwards pointed out, as you can see further than one car ahead and plan accordingly. That said, adaptive cruise is still available to you under these conditions, whereas it would be unsafe to engage standard cruise.

If you're just cruising in the open country, with no other vehicles around, it really doesn't matter which one you use (as pointed out by @U-235). The hypothesis by @392DCGC that the acceleration profiles between the two systems are the same seems plausible.

 

[ExcursionDiesel]

I've noticed what @SpeedyV said. Adaptive Cruise will apply braking on approach to slower vehicles. Setting the Adaptive distance to max helps. One must change lanes much earlier to avoid this. Also, Adaptive Cruise will speed up more aggressively which is another waste of fuel.

The truth be told, leaving Cruise off altogether is your best bet for economy.