If the design engineers and engine manufacture say you can ... You can, within specs. Gas, diesel, or whatever. They wouldn't sell many MH's if you couldn't go up and down mountains.
Some people need to be to the top of the hill first. Just waive at them as you pass them at the next gas station.
Select the right gear on descent and let the engine do the work, only stab the brake to slow as needed, maybe a lower gear is needed at that time where speed is constantly building. Most of the time you could probably descend without using them at all.
