Does pushing in the clutch while going downhill saves fuel?

along with all of the other answers, you can also destroy your clutch brake by pushing the clutch completely to the floor while the truck is moving.. but this is really dangerous!!

 

The momentum of the truck rolling down the road spins the tires, axle shafts, ring and pinions, universals, transmission, and then to the engine. As part of the governing system, it will go to no fuel above a certain RPM with the throttle at idle. As it approaches idle speed, it'll slowly work the fuel back in. This is why you don't notice it (except a two stroke Detroit with the governor bump). The idle fuel consumption is just that-fuel consumption at idle. As far as where it goes when it's not injected, it'll go through the return line. If it didn't shut fuel off, your engine would take a month to return to idle (like I said, it'll slow down as fast as a 6V92 will speed up going up hill), and when you turned the compression brakes on, you'd be spitting raw fuel out the exhaust.

 

Aggressive? I was the only one to give the OP the correct answer. I was not advising him to employ the tactic just telling yes it can save fuel and then adding it was illegal and can be very dangerous.

I have not backed down from my claims despite all the objections from all the subsequent posters who seem to be angered by my truthful answer. Holding to one's convictions despite resistance and criticism is something that a man does. Retreating from them when criticized is an act of a coward. I seriously thought you would know this. The more you post the more is revealed about you and the less I respect you. I thought you would know the attributes of a man but apparently you don't.

I was not advising him to employ the tactic just telling yes it can save fuel and then adding it was illegal and can be very dangerous.

Perhaps I was unclear on this, which is my bad. I have, on two occasions had symptoms that I found alarming. These symptoms can be associated with a heart conditions. So because I was concerned I went to the ER to get checked out and was tested as protocol when a patient comes in with those symptoms. I have had other tests because I pushed the doctors to authorize the tests. There is no one more concerned about my health than me so even though the doctors saw little need for most of the tests I wanted answers and they obliged me to okay tests that might give me peace of mind. The heart cath that I'm having tomorrow is one that is elective and I agreed to for my own peace of mind. The doctor told me my chest pain last week was a muscle strain and fully expects the cath to show what every other test has shown: a very strong, well functioning heart with no blockages or abnormalities.

I have been discharged with no physical restrictions whatsoever. I am free to run, lift weights, swim, drive, etc. Illegal? Can you please cite for me a rule in the FMCSA handbook that shows I am driving illegal because I sought medical screening for some concerns I had?

Do you want to make that call? That's fine by me. You would be the one looking like the jack-arse. I have reported every symptom, every visit to the ER and kept them totally in the loop every step of the way. After each visit the doctor was required to fill out a form stating that I was safe and fit to drive a CMV. And each time they have done that with no reservation.

You seem to be rushing to judgement about my character, my driving professionalism and my knowledge based on what? A couple posts made on an internet forum in which you disagree with?

You don't know my driving record or the manner in which I drive. You have shown yourself to draw all kinds of conclusions about me personally, including my personal health which you know nothing about other than what you misconstrue in reading my posts.

Before I got my class A license I drove all kinds of Class B CMVs in busy cities on the city streets, in tight alleys in high pedestrian traffic areas often making more than 100 deliveries per day in a fast paced environment. My record? 17 years without a preventable accident.
During those 17 years I received many safe driving awards and bonuses.

Just because I gave an answer that differs from yours doesn't reveal all the things that you are claiming about me. You do not know me at all. To get so personal and repeatedly accuse me of lying, however, is rather revealing about you .

 

That's the first statement you made that was true. I think you're an unsafe know-it-all that lacks any good sense. You have no creditability to back what you say when you change your statementa after people call you out. But you make it so easy for me to draw my conclusion. You're a waste of time and I hope the new drivers can see that as well. Don't worry, there will be no more from me because I'm sure others will have some things to say.

 

That's a very wise decision on your part.

 

This thread has outlived it's usefulness. Devolved to the point it should just get shut down before some newbie barrels down the grapevine trying to save an ounce of fuel.

 

And unless I missed it, nobody even mentioned what happens to the engine, clutch, transmission and/or driveline if the clutch is engaged at a speed in excess of the gear in use.

Just don't do this, Georgia Overdrive is a fool's game.

 

Any fuel advantage gained by coasting down a hill, whether the transmission is in a gear with clutch depressed or completely out of gear, is lost by the incredible risk to life and property. I don't care what the laws of inertia and gravity have to say about it.

Those same laws apply to the ability to stop a vehicle. As said before, accelleration is optional. Stopping is mandatory. You will stop one way or another. The difference is in having a choice of how that stop will be made.

^^^This^^^ almost sounds like a threat.

 

There's a great article in PopularMechanics last month I think talking about this very subject. That's where I learned fuel injectors close up when going down hills.

 

I guess I'm not the only one that thought that.