2010 GMC Acadia Owner's Manual - Page 264

9-8 Driving and Operating Highway Hypnosis Always be alert and pay attention to your surroundings while driving. If you become tired or sleepy, find a safe place to park your vehicle and rest. Other driving tips include: ... Hill and Mountain Roads Driving on steep hills or through mountains is different than driving on flat or rolling terrain. Tips for driving in these conditions include: . { WARNING Coasting downhill in N (Neutral) or with the ignition off is dangerous. The brakes will have to do all the work of slowing down and they could get so hot that they would not work well. You would then have poor braking or even none going down a hill. You could crash. Always have the engine running and the vehicle in gear when going downhill. Keep the vehicle serviced and in good shape. Check all fluid levels and brakes, tires, cooling system, and transmission. Going down steep or long hills, shift to a lower gear. Keep the vehicle well ventilated. Keep interior temperature cool. Keep your eyes moving - scan the road ahead and to the sides. Check the rearview mirror and vehicle instruments often. . . . { WARNING If you do not shift down, the brakes could get so hot that they would not work well. You would then have poor braking or even none going down a hill. You could crash. Shift down to let the engine assist the brakes on a steep downhill slope.