disengaging clutch vs putting in neutral

Discussion in 'Fuel Economy' started by stargift, Jul 10, 2008.

  1. stargift

    stargift Member

    I always push in the clutch pedal while going downhill with my 2006 scion xb 5-speed and I get great mpg. Someone said that I should just put it in neutral otherwise I will be wearing out some component of my cluth. Is that correct?
  2. applemac*fit

    applemac*fit Well-Known Member

    Yes - you'll wear out your throw-out bearing, and possibly more.
  3. kmactavi

    kmactavi Well-Known Member

    That's not correct, actually by leaving the clutch in and remaining in gear you're saving a (tiny, imperceptible) amount of wear to your clutch. When you let out the clutch in neutral, the clutch has to spin up the input shaft to the transmission, so there is a bit of wear. Note that I'm not a very reliable source for this, but as far as I know, that's what happens. If you want to read, here you go.

    I put it in neutral because my glides are usually long and my leg would get tired holding the clutch in for over half of my driving. :D

    edit:Just saw Applemac's post, he knows more about it than me, but I would say that the wear would be on the throw-out bearing, not the clutch? Anyway, shifting to neutral is probably the best.

  4. kwj

    kwj I hypermiled this

    Here's another consideration, if the hill is steep enough that you gain speed and have to use your brakes, it might be better to leave it in gear and stay off the gas pedal. Your engine can help keep your speed down, and since you'd be in fuel cutout, you'd actually be saving more gas than when in neutral.

    In many states, it is illegal to coast down inclines in neutral, perhaps a holdover from before synchromesh transmissions, but if you are going to go into neutral, try releasing the gas and nudging the shifter out of gear. If you do it right, it is gentle and smooth, and does not involve clutching or throwout bearings.

    And if you wanted, you are just a key back and forth from a FAS.

    Of course you'd have to depress the clutch to reengage the gears, and if you went into a FAS you'd bump start in fifth gear (or 6th if you've got it), select the appropriate gear and you are on your way.

    Of the three techniques, the FAS would use the least gas, by shutting down the injectors and also providing the best glide.

    Depending on traffic, and other conditions, the engine "on" and tranny in gear, but the foot off the gas, would probably provide the next best MPGs, since you'd be in fuel cutout until you got down to idle RPMs.

    The third method, of simply bumping into neutral would burn a little fuel because your engine would settle down to near idle RPMS.

    Different situations may warrant different choices. But you'll learn which are best for any given day or time of day.
  5. abcdpeterson

    abcdpeterson Well-Known Member

    I agree. I helped replace a throw-out bearing in a friend’s car in high school. I don’t think that bearing is meant to take excessive extended wear.

    The clutch is held closed by a spring loaded system, which is spinning with the clutch. To release the clutch you need to counter act the springs, but there moving. There is a stationary fork your moving with the clutch peddle to release the spring pressure. The bearing is on the end of that fork, normally just sitting there – not spinning. The bearing provides a way for you to move the spinning clutch system with a stationary lever.
    If I am sitting at a light that just turned red, I will often put the car in neutral and take my foot off the clutch.

    Note: I OFTEN cost keeping my foot on the clutch, just not for extended(excessive) length of time.

    But costing in neutral:
    Costing (down hill) in neutral here in Minnesota is illegal. I used to drive a truck, and I have experienced why it’s illegal. In the truck if I accidentally missed a gear and got stuck in neutral the only way to hit the gear was to rev match the engine to the speed. Rev matching can be done, but (more so in a truck) while doing that you don’t have the engine’s help controlling the speed of the vehicle.

    Note: I OFTEN cost in neutral in my car. 1 I can easily slow my car with the breaks – without the engines help. 2 my transition is better than that truck have not had a problem getting back into gear.
    In most cars if your trying to put the transmission in an speed appropriate gear you should not have much if any trouble.
  6. I have a long (over 1.5 miles) down hill run on my commute with a stop at the bottom. I leave the car in 5th and shut off the key. This provides vacuum for the power brakes. Just before the stop at the bottom just turn the key back on and it is running for the next pulse. Only turn the key back one position to accessory. On less severe glides I turn the engine off the same way only I use neutral. I restart in 5th for the next pulse. Save on!
  7. Neddy Seagoon

    Neddy Seagoon Active Member

    Hi, first of all do not keep the clutch in for any extended period of time as you will wear out the release bearing. The only way to change the bearing is to remove the gearbox, not a job you want to do too often. Just pop the car into neutral then when ready back into gear. Good luck.
  8. kmactavi

    kmactavi Well-Known Member

    me and my metro: I'm pretty sure that even in ACC safety equipment is not operational. Also, even if it does work in your metro, don't recommend it to anyone else, since disabled airbags are not a good thing. My manual warns about coasting with the car off in gear, it says fuel could get in the catalytic converter and damage it.


Share This Page