cyber3d

So, anyone know what is best for tackling this situation? Here in Southern California we have a few really long downhill grades. Including the "grapevine" and the 101 grade into Camarillo.

The consensus with my other car (Jaguar) is that downshifting is recommended. What about our GLC300?

mdsbuc

Should be the same, unless you like spending $$$ on brakes.

Mickfx

From the manual - breaking in first 1000 miles:

"Do not manually shift to a lower gear to brake the vehicle."

Of course, you're not supposed to do any hard braking on new brakes either, so tough call. I'd probably ride the brakes and not screw with the engine. I broke in every car I ever owned except for one, because I had to drive cross country 2 weeks after purchase - so very little variation in engine speed, although I tried. I had alll sorts of problems with that engine and it was a Honda - not known for engine issues. Brakes & rotors can be replaced.

dieseldoc

Use brakes rather than downshift.

mdsbuc

Per Ray Magliozzi of Car Talk:

"The primary reason to use a lower gear is safety. When you’re riding your brakes for a long period of time, all that friction turns into heat, which can overheat your brakes and cause them to fail. And traveling down the mountain without brakes won’t be good for the vehicle either"

Full article:
http://www.yankton.net/life/article_...93eafecea.html

In this MB video, check the comment beginning at the 4 minute point:

JEVA

I agree that if you can avoid it, use the brakes...brakes/rotors are cheaper than engine overhaul. Although if you are leasing, you probably aren't concerned about the long term viability of the engine

Mickfx

Outside of the break-in period, engine braking is the way to go but during the break-in period, I'd ride the brakes....or take a different route.

mdsbuc

There's a big difference in using engine compression to slow the vehicle down from one speed to a much lower one, multiple tapping the downshift paddle, bap, bap, bap, in quick fashion, vs. braking to the speed you want to descend the hill, then placing the car in the proper gear to maintain that speed after you have braked. The latter is the way to go, and quite proper. It's gentle on the transmission and the engine.

JEVA

As long as it doesn't maintain a relatively steady engine RPM for extended periods or push the RPMs way up.

OhioRiderAaron

I'd continue with the same method you use with the Jaguar. Downshifting to help maintain a safe speed through the mountains is my recommendation. The GLC brakes are pretty decent size, but the brake pad compound itself probably can't withstand the extra heat generated. Brake fade is the result. The transmission can withstand the work, don't worry!

newmbguy1

I agree with others downshift (gently). Don't do what I did with my lease cars. If within break in period ride the breaks.

Totally unrelated but wanted to add if hybrid car just ride the breaks. You're using the electric motor to slow down anyway.

B2FiNiTY

downshift with the added use of brakes if needed.