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Discussion Starter · #1 ·
We just arrived at our favorite place in the Colorado Rockies. 800 plus miles and averaged 25.1 mpg. I'm happy. It handled the uphill without breaking a sweat.

Now for my question. My wife looked thru the manual for how to manage some of the long downhill runs we will be doing. We usually have my diesel truck which has an engine exhaust brake so going downhill is not an issue. The signs on the highway say to use a lower gear to retard the engine and help with braking. From what we could determine the downhill braking in the manual referred to slow speed off road stuff. It's not mentioned in the manual, at least I couldn't find it, but would putting the transmission in the manual mode serve the same purpose? One drive we will take will have about 10 miles of all downhill. Don't want to burn the brakes.
 

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I use adaptive cruise when going downhill. It manages engine braking and real braking better than I can. Alternately, use the paddle shifters to shift to a lower gear. I do this on roads that are too windy for cruise.
 

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ACC does a great job at downshifting for you and then applying the brakes as needed. It may give you a false sense of engine braking ability since you can’t always tell when the brakes are applied, though. On twists and turns where you may want to accelerate and slow down, the manual shifting mode would be the way to go in my opinion.
The downhill mode in xmode is only for slow speed so it’s not very useful on an actual road.
 

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Yup, slot the stick over into manual mode and downshift using the left paddle as-necessary.

ACC really does a great job of maintaining speed and mitigating distances to the preceding vehicle, but like xydadx3 noted, unless you're used to using it, it may not give you a sufficient feedback when the driving is more demanding.

Through the mountains of WV, I loved the ability to manage speed by using the paddles in manual mode. I know that there's a lot of braking power in-reserve, but still, it just gives me more peace-of-mind to downshift - and besides, the increased level of interaction with the vehicle also allows me to pay better attention to the task of driving. :)
 

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I would absolutely switch over to "manual" and use the paddles to select "gears" to utilize engine braking.

You might be able to get away with keeping it in auto and using the paddles to engine brake as well, as long as you don't give it any gas until you no longer need to engine brake. That's what I do when cruising through the Appalachians and foothills where the road swiftly transitions from climbing to descending. For long Rocky Mnt. downhills, keeping it in "manual" might be a simpler option.
 

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Discussion Starter · #6 ·
Did 2 long downhills today. I was able to use the adaptive cruise some which worked great except on some of the hairpins it would lose sight of the vehicle in front of me and start accelerating. I found "4th" gear to be the best setting otherwise. Thanks for the help.
 

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Did 2 long downhills today. I was able to use the adaptive cruise some which worked great except on some of the hairpins it would lose sight of the vehicle in front of me and start accelerating. I found "4th" gear to be the best setting otherwise. Thanks for the help.
Good point!

This is definitely something for folks to be aware of.

Steep hills are also another potential problem area for EyeSight.

Thank you for bringing up this important point, JDT!

For all newcomers to Subarus with EyeSight and Adaptive Cruise - please exercise increased caution in using ACC until you've become familiar with its quirks!
 

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2nd this

the more you drive the more you’ll learn the limitations of the car’s systems. Overconfidence in them can lead to unsafe situations if the driver doesn’t react when needed. The more you know!
 

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Exactly why I treated the car as if it didn't have any safety stuff and then slowly worked the tools into my daily driving to learn how they react in a way that kept me over-cautious until I became aware of how they operate. Even now I'm not entirely confident when using ACC and the cars in front of me slow down too quickly. I've had a couple situations where the anit-collision kicked on because of the cars in front stopping abruptly, and I'd rather take over before that happens and slow down more sedately myself. On a curvy, hilly road I wouldn't use ACC at all, to be honest. I'm sure it will do fine the vast majority of the time, but it's the outliers that lead me to maintain full manual control in those conditions. Doesn't hurt that I find those kinds of roads fun to drive myself :) For the hilly curvy roads, it's paddle shifters and full control for me.
 

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Exactly why I treated the car as if it didn't have any safety stuff and then slowly worked the tools into my daily driving to learn how they react in a way that kept me over-cautious until I became aware of how they operate. Even now I'm not entirely confident when using ACC and the cars in front of me slow down too quickly. I've had a couple situations where the anit-collision kicked on because of the cars in front stopping abruptly, and I'd rather take over before that happens and slow down more sedately myself. On a curvy, hilly road I wouldn't use ACC at all, to be honest. I'm sure it will do fine the vast majority of the time, but it's the outliers that lead me to maintain full manual control in those conditions. Doesn't hurt that I find those kinds of roads fun to drive myself :) For the hilly curvy roads, it's paddle shifters and full control for me.
Not to mention this is not the intended purpose of the eyesight system or ACC. Although it works great 95% or the time, it isn't a substitute for an astute driver.
 

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I could swear that I read in one of the manuals that you shouldn't use cruise control (ACC or regular) on long, steep downhills because the Ascent will apply the brakes to maintain the set speed, potentially overheating them. Does anyone else remember seeing that or am I imagining it?
 

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I’ve made 2 round trips between Denver and Grand Junction in the pass month using I-70. Every time I was going down the steeper grades I switched to manual mode and downshifted to stay off the brakes and it worked great.
 

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^ Ain't that the truth.

I'll admit to being one of such individuals, too.

That said, I don't (and I don't think I ever will) completely trust the lines of code: I monitor the vehicle even more closely, it seems, when I'm using any of the driving assists. :)
 

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I prefer to use the paddle shifters when I need engine braking. Depending the length of the hill and how consistent it is, sometimes I don't put in manual, I just tap the "-" paddle until I get the engine braking I need. It will stay in the lower gear until you, or the cruise control, add throttle, then it will switch back to auto mode.
 

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Oh I definitely use ACC in places that are not recommended, I just don't use it for the express purpose of engine braking / downhilling.
 

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Discussion Starter · #18 ·
Is there a secret to getting the paddle shifter to respond? Yesterday on a downhill run from Estes Park to Boulder I would tap it but nothing would happen. It would show 7 and just stay there. I did have it in the manual mode. Sometimes I could get it to 6 or even 5 but it was very inconsistent.
 

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Is there a secret to getting the paddle shifter to respond?
No secrets or special tricks; just pull the paddle shifter toward you and release. As long as your RPM's aren't already too high it should downshift or too low for upshifting.
 

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JDT, you may need to pull the lever in towards you (pull towards the rim of the steering wheel, kinda like you'd flash your high-beams or to engage the wipe/mist on the other stalk) more firmly. The lever that you pull (downshift on the left, upshift on the right) will click inwards with a feeling similar to how a torque-wrench breaks or how the classic electronic game of "Simon" registers your selection. :)

Don't worry excessively about selecting a gear too low or too high. As xydadx3 noted, if an incorrect selection is made, the vehicle will emit warning beeps to let you know that you've exceeded the threshold of what it's able to give you. The system won't let you cause any mechanical damage.
 
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