Does Cruise Control use brakes for slowing down?
 

I am wondering and I never had a chance to test this at night.

Depends. If you hold the stalk down it will start dropping MPH in large increments and then yes, it uses the brakes. Just giving it a tap down an MPH or 3 though won't use them.

Won't it also use them if you start to pick up speed while going downhill? Feels like it anyway....

I've noticed something happening on our '06 A6 when going down a long hill with the cruise engaged. I can hear a noise (almost sounds like the ABS pump firing) and then the car begins to slow just a bit. I've experienced it more than once, something is happening in the background, I'm not certain what it is.

I know our previous MBz wagon would actually downshift one or two gears when the car was in over-run and picking up too much speed. I really dis-liked that design. I ended up turning off the cruise control if I could see I was approaching a long downhill section.

If the hill is steep enough to gain enough speed, yes it will.

Yes 100%. I use mine daily. When going down a steep hill at night I can see the third brake light going in the rear window.

Why do you dis-like this? It is the correct way to maintain a low speed, whether in an automatic or manual.

It helps with efficiency to just let the car pick up speed and coast back down to the cruising speed.

Yes, but the car cannot tell how far a hill will go, if there are perhaps curves coming up where it might be dangerous to assume it can go faster than it was set to, etc. It's a car, not a subsitute for a person, so they program it to do the best they can with the availible tech.

I guess the primary reason was the car was still new to us and the downshift (5 to 4) was quite harsh. In all seriousness, I thought the trans was ready to fail. Then it shifted from 4 to 3 and I was really concerned as I had never witnessed this on any car before. It just wasn't natural. I saw it do it again and again during the time we had that car when traveling on the highway on a fairly steep downgrade. I got into the habit of switching the CC off when I could see it coming.

Also, as blackhawk mentions, it's a waste of energy when the car tries to slow itself.

I wonder if the Germans have something in their regs that mandates this sort of behavior when the car is on cruise ??

xx km/h over set speed = apply brakes :cool: