A post in an August 14, 2017 Reddit feed reveals [edited]:
I was driving on the I-15 into Scipio, UT down a long and steep highway. I shift my Jetta into neutral and coast down the hill at 85 mph (speed limit is 80). I noticed a tractor trailer behind keeping up with me. So my question to truckers: Is it common for you all to shift into neutral and if you do, how fast are you willing to go before tapping on the brakes?
Following are a few of the [edited] responses:
- I’m not familiar with that specific hill, but truckers shouldn’t be going down hills in neutral. They should pick a gear and use that to control their speed. They should absolutely not rely on their brakes, as they will get extremely hot quickly and not function.
- If you’re going downhill you don’t need to go into neutral to hit 80 mph. The weight alone can push you that fast.
- When going down hill I usually shift into neutral and let gravity bring me up to 88 mph. Then I switch on the Flux Capacitor and attempt to go back into the Old West where my Truck will rule the world of Freight Hauling and I will become a billionaire.
- The truck was definitely not in neutral or he’d have been going much faster than 80 mph on the way down. 80,000 lbs is a lot of weight. Unchecked, it pushes us down hills rather quickly. It’s actually illegal for us to coast in neutral like that 🙂
- If I go up the hill in 10th gear, I’ll usually go down in 10th (or 9th depending on how big the hill is). Rule of thumb is to go down steep hills one gear lower than the one you went up in and let the engine brake control your speed so you minimize use of the brakes altogether or as much as possible. If it’s a straight downgrade and dry conditions, I try to keep my max speed no more then 70 mph. No one in a truck should be coasting down a hill in neutral -“ it’s dangerous!
- Never. Not only is it not safe, you actually use more fuel. I assume you do this to save gas. You are in fact using more gas. Any time you are coasting off the gas petal, you are using 0 gas as long as you are in gear. The momentum of your car is spinning the engine, not the gas. Once you kick your car out of gear, you are using gas to idle the engine. It’s a very common misconception.
- The engine is a truck’s primary brakes. They also aren’t synchronized like cars. That being said, going down a hill in neutral is how you die in a truck.