Sorry, but that's totally not true! There is no way, at least on many of the mountain roads I've driven, that you can stay off the brakes long enough for them to significantly cool! If you live in mountainous areas and drive roads that have long downhill sections, it is
definitely preferable to keep the car in a lower gear, one that's appropriate for the speed you're traveling, and let engine compression help keep the cars speed in check. It absolutely will not hurt the engine or transmission and it will go a "long" way toward extending the life of the brakes.
I was on a trip in Colorado, descending from Slumgullion Pass when we started smelling a "very" harsh/acrid odor. This smell would come and go but when it hit you, it was like hitting a brick wall. The farther down the mountain we went, the worse the smell got. This went on for a little over 5 miles. Anyway, we finally caught up with the culprit. It was a Buick with a couple of little ol ladies in it. The driver had ridden her brakes all the way down that mountain pass and had totally cooked them. When we pulled into the next town, she turned into a local restaurant and as we passed, you could see her front brake disks were glowing red! :SHOCKED: In case you didn't know, that
is not a good thing. At the speed she was traveling, she could have manually shifted into D2 and let engine braking control the speed of the car and she wouldn't have cooked her brakes in the process.
Bottom line is, it doesn't matter what kind of vehicle you're driving. Truck, car, or motocycle, if you've got a long downhill section to travel it is totally appropriate to use engine braking to help control the speed of the vehicle.
This is also a misconception. Manually shifting an automatic transmission doesn't put any more wear and tear on the transmission than letting it shift automatically does! That's provided the driver is shifting into a gear that's appropriate for the speed the car is traveling. If you abuse the system, you're going to have problems but, to use an example related to what I posted above, if you shift into 2nd gear at around 30 mph on that downhill run to help control the cars speed with engine braking, you won't be hurting a thing.
FWIW!
Drive Safe,
Steve R.