Adaptive Cruise Contol

[Rjhagner]

Is it true that gas mileage suffers when using ACC? I also see the owners manual states that ACC should not be used when towing....anyone know why that would be?

Thanks

 

[Rototerrier]

1) Gas Mileage suffers because ACC or any cruise control in general aggressively tries to maintain the speed you've selected. It doesn't handle the subtle things your right foot does when you speed up a little down a hill to not have to give more gas to go up the next hill. You do that naturally. It just tries to maintain the set speed and doesn't do anything to adapt to the terrain. The adaptive part makes it even crazier. Once it locks in on the vehicle in front of you, it aggressively tries to maintain that distance and will surge the throttle quite a bit if the vehicle in front of you drives like an idiot. You would adapt to that behavior and let off a little to maintain a distance without trying to keep things perfect. All these things will result in worse fuel mileage. Wifes Q7 has cruise control settings and you can adjust how aggressively it tries to maintain speed. On the least aggressive, it will swing +/- 5 mph which helps maintain good fuel economy. It's kinda weird though, so I don't do it. I leave it where it maintains, otherwise folks behind me will go nuts. No one likes those types of speed fluctuations, but that's what it takes to not kill mileage with cruise.

2) ACC with a trailer...I've done it and it works fine in a wide open environment. I would NEVER do it in traffic. ACC without a trailer will sometimes brake so late that the collision warning comes on. If you had a trailer, I suspect it might result in an actual crash. My wife's Audi Q7 has NEVER stopped so late that it triggers a collision warning. My truck has done this several times. The ACC software needs some work and, for that reason, you should never tow with it...and if you are an idiot like me that doesn't always follow directions, only do it when there's no traffic and you are paying attention and in a wide open section of interstate. I really do think it will kill someone pulling a trailer...especially if the trailer doesn't have brakes. The truck wouldn't be able to stop and will probably lock up trying not to rear end someone.

 

[Rjhagner]

1) Gas Mileage suffers because ACC or any cruise control in general aggressively tries to maintain the speed you've selected. It doesn't handle the subtle things your right foot does when you speed up a little down a hill to not have to give more gas to go up the next hill. You do that naturally. It just tries to maintain the set speed and doesn't do anything to adapt to the terrain. The adaptive part makes it even crazier. Once it locks in on the vehicle in front of you, it aggressively tries to maintain that distance and will surge the throttle quite a bit if the vehicle in front of you drives like an idiot. You would adapt to that behavior and let off a little to maintain a distance without trying to keep things perfect. All these things will result in worse fuel mileage. Wifes Q7 has cruise control settings and you can adjust how aggressively it tries to maintain speed. On the least aggressive, it will swing +/- 5 mph which helps maintain good fuel economy. It's kinda weird though, so I don't do it. I leave it where it maintains, otherwise folks behind me will go nuts. No one likes those types of speed fluctuations, but that's what it takes to not kill mileage with cruise.

2) ACC with a trailer...I've done it and it works fine in a wide open environment. I would NEVER do it in traffic. ACC without a trailer will sometimes brake so late that the collision warning comes on. If you had a trailer, I suspect it might result in an actual crash. My wife's Audi Q7 has NEVER stopped so late that it triggers a collision warning. My truck has done this several times. The ACC software needs some work and, for that reason, you should never tow with it...and if you are an idiot like me that doesn't always follow directions, only do it when there's no traffic and you are paying attention and in a wide open section of interstate. I really do think it will kill someone pulling a trailer...especially if the trailer doesn't have brakes. The truck wouldn't be able to stop and will probably lock up trying not to rear end someone.

Thank you Rototerrier for the excellent explanation! It is much appreciated.

As much as I enjoy ACC, I may use it a bit less frequently in an attempt to save mpg. Regarding towing my camper, I’ll stick with regular cruise control when the road allows it.

 

[Johnvan]

I used it a bit while towing. The problem was on steep downgrades. I couldn't tell if it was riding the brakes so I stopped using it when going downhill. Regular cruise is fine downhill, it down shifts and doesn't brake.

 

[SpeedyV]

1) Gas Mileage suffers because ACC or any cruise control in general aggressively tries to maintain the speed you've selected. It doesn't handle the subtle things your right foot does when you speed up a little down a hill to not have to give more gas to go up the next hill. You do that naturally. It just tries to maintain the set speed and doesn't do anything to adapt to the terrain. The adaptive part makes it even crazier. Once it locks in on the vehicle in front of you, it aggressively tries to maintain that distance and will surge the throttle quite a bit if the vehicle in front of you drives like an idiot. You would adapt to that behavior and let off a little to maintain a distance without trying to keep things perfect. All these things will result in worse fuel mileage. Wifes Q7 has cruise control settings and you can adjust how aggressively it tries to maintain speed. On the least aggressive, it will swing +/- 5 mph which helps maintain good fuel economy. It's kinda weird though, so I don't do it. I leave it where it maintains, otherwise folks behind me will go nuts. No one likes those types of speed fluctuations, but that's what it takes to not kill mileage with cruise.

2) ACC with a trailer...I've done it and it works fine in a wide open environment. I would NEVER do it in traffic. ACC without a trailer will sometimes brake so late that the collision warning comes on. If you had a trailer, I suspect it might result in an actual crash. My wife's Audi Q7 has NEVER stopped so late that it triggers a collision warning. My truck has done this several times. The ACC software needs some work and, for that reason, you should never tow with it...and if you are an idiot like me that doesn't always follow directions, only do it when there's no traffic and you are paying attention and in a wide open section of interstate. I really do think it will kill someone pulling a trailer...especially if the trailer doesn't have brakes. The truck wouldn't be able to stop and will probably lock up trying not to rear end someone.

If it’s braking that late on you, you’re likely either (1) not setting it to leave enough car lengths between you and the vehicle in front of you, or (2) using the ACC in situations where traffic comes to a complete stop far enough ahead that your radar hasn’t picked up on the slowdown. Either way, that can be dangerous, as the system can only compensate so much.

That said, I completely agree about trailering. Drivers with trailers need to be decelerating and/or braking well in advance of the distances ACC would activate.

 

[Jus Cruisin]

I could see the ACC get you in trouble in the wet. Mine hits the brakes pretty hard occasionally and that could lead to jackknifing a trailer.

 

[Rototerrier]

If it’s braking that late on you, you’re likely either (1) not setting it to leave enough car lengths between you and the vehicle in front of you, or (2) using the ACC in situations where traffic comes to a complete stop far enough ahead that your radar hasn’t picked up on the slowdown. Either way, that can be dangerous, as the system can only compensate so much.

That said, I completely agree about trailering. Drivers with trailers need to be decelerating and/or braking well in advance of the distances ACC would activate.

I'm not the only one. This forum has many examples of folks having the same late braking acc tendencies. Compared to BMW, Mercedes, Audi, and even my old 2017 Honda CR-V, the acc on this truck suck big sweaty gonads. And that's just the gods honest truth.

 

[Gondul]

The ACC isn't anywhere near as smooth and seamless as the system on the wife's Fozzie...

 

[Han Ridge]

I recently returned from a 5000 mile trip with a 6000lbs TT. ACC had little effect on flat highway but once you hit hills it did effect mileage. ACC does not take advantage of momentum gained on down hill runs. One thing I did a lot is to find a big rig doing my same speed and pull in behind it which cuts a lot of air. I saw as much as a 1.5 mpg gain doing this.

 

[jeffmc306]

I wonder if anything has changed on the 2019 HD 2500's because they state on the website's "Safety & Security" tab that Adaptive Cruise works "even with a trailer attached". It also has the same wording under Forward Collision Warning with Active Braking.

2023 Ram 2500 Safety & Security | Airbags & More

Explore the safety & security features of the 2023 Ram 2500. Discover the high-strength steel frame, airbags, available forward collision warning & more.

www.ramtrucks.com

Makes you wonder if the Marketing guys are making this stuff up or did the engineers improve the systems so they're compatible with a trailer? I'm upgrading from a '19 Ram 1500 and would really like to know! Gondul, what do you think?

 

[Gondul]

The 2500 is at the dealer and I can't pick it up until Saturday!

I if the ACC is anything like the 1500 then you are probably ok if you are on a long, flat, straight section of road, I just find the system to be a little too abrupt for my liking.

Yeah, there were several things 'promised' that are have been delayed, like the AUX camera hookup and the TTPMS. Someone ordered the AUX Camera stuff from MOPAR and he says he received a ship notification... now to see if it is an easy install, or it will need to be taken to the dealer.

 

[jeffmc306]

The 2500 is at the dealer and I can't pick it up until Saturday!

I if the ACC is anything like the 1500 then you are probably ok if you are on a long, flat, straight section of road, I just find the system to be a little too abrupt for my liking.

Yeah, there were several things 'promised' that are have been delayed, like the AUX camera hookup and the TTPMS. Someone ordered the AUX Camera stuff from MOPAR and he says he received a ship notification... now to see if it is an easy install, or it will need to be taken to the dealer.

That’s great news about your truck! Saturday is just around the corner We expect a full photo gallery over on the HD Forum!
I’m still waiting to hear from my salesperson on the status of a ‘19 Ram 2500 at another dealer in Milwaukee so fingers crossed.

 

[Jello0123]

I noticed that if you turn on the ACC while towing it automatically adjusts to the farthest away setting for the vehicle in front of you. This is a nice safety feature since we do need more distance to slow down. I haven't used it much while towing but it is definitely better than "regular" cruise control.