So I was driving to Staples with my mom, We were in my brothers car, which is manual. When we exited off the freeway, I put it into neutral and just let it coast. She said I shouldn't do that cause it ruins the clutch, and I should always keep it in gear, and just downshift when slowing down.

Is this true? "coasting" ruins your clutch? cause I always do it in my accord, whether it's cause I'm going down a hill, or I'm about to slow down, I put it into neutral. I figured it saves gas since, but if it ruins my clutch I'll change my driving habits.

Thanks,
-Nate

False

it does not ruin your clutch, but as a rule of thumb you should stay in gear as much as possible. you should pretty much only be out of gear when shifting (duh) and at a complete stop.

you are actually burning more gas by doing that by slowing down in neutral. when you are slowing down (ie foot off the gas), the car being in gear will use absolutely NO fuel at all, while coasting in neutral requires fuel to keep the engine running at idle. this is known as DFCO (deceleration fuel cut off).

hmm so putting it in neutral to coast around curves and turns would not save gas? a friend was tryin to recommend it to me. i thought when the car was in neutral, the gas is cut off. i learned somethin new today =)

it does not ruin your clutch, but as a rule of thumb you should stay in gear as much as possible. you should pretty much only be out of gear when shifting (duh) and at a complete stop.

you are actually burning more gas by doing that by slowing down in neutral. when you are slowing down (ie foot off the gas), the car being in gear will use absolutely NO fuel at all, while coasting in neutral requires fuel to keep the engine running at idle. this is known as DFCO (deceleration fuel cut off).

That's all true. Plus putting it in neutral causes you to use your brakes more so they'll wear faster. Not to mention that it's not really safe because if you have to speed up for some reason it takes you a split second longer since you have to put the car back in gear. And as we know sometimes all it takes to get in (or avoid) and accident is a split second.

But the OP's question is if if will ruin his clutch. It wont damage it's clutch in any way, it's just not a good driving practice.

A general rule of thumb is to leave it in gear until the very last second of the car about to stall when stopping. As was mentioned, you always want to be in gear for safetys sake.

And yes you'll be burning more gas and have to use your brakes more (rev match the downshifts to use engine braking).

I'm quoting this from another forum called Ecomodder
http://ecomodder.com/forum/showthread.php/dfco-3019.html

"How to tell if your car has DFCO

Be careful with this test as you may lose Power Steering and Power Brakes during it! Choose the right time and location to perform the test.

On any level or slightly downhill road get up to at least 40 MPH, then start engine braking by keeping the vehicle in gear and letting all the way off the throttle while keeping the clutch disengaged (MT) or keeping the transmission in a gear lower than D (AT). Notice the deceleration force and the sound of the engine.

Now tun off your ignition (This is where you may lose your PS/PB, so be wary!) and watch for any harsher deceleration or change in the pitch of the engine for a few seconds.

If nothing was any different with the ignition turned off then your vehicle uses DFCO. If it decelerated at a different rate or pitch with the ignition off then it does not use DFCO. Do not forget to start your engine back up! But, do not try to start your engine back up (with the starter motor) while the car is moving and in gear. Just putting the key on run will cause the engine to "restart" "

So I was driving to Staples with my mom, We were in my brothers car, which is manual. When we exited off the freeway, I put it into neutral and just let it coast. She said I shouldn't do that cause it ruins the clutch, and I should always keep it in gear, and just downshift when slowing down.

Is this true? "coasting" ruins your clutch? cause I always do it in my accord, whether it's cause I'm going down a hill, or I'm about to slow down, I put it into neutral. I figured it saves gas since, but if it ruins my clutch I'll change my driving habits.

Thanks,
-Nate

When you shifted into neutral, do you release the clutch pedal? If so, then your mom is incorrect. However, if you are keeping the clutch pedal pressed, then you are going to wear your clutch quicker.

When you shifted into neutral, do you release the clutch pedal? If so, then your mom is incorrect. However, if you are keeping the clutch pedal pressed, then you are going to wear your clutch quicker.

What he said. If you keep the clutch down then you are wearing your clutch bearings. Same reason why at a traffic light you should shift into neutral and release the clutch.

As for the whole deceleration thing...best to keep the car in gear. From my understand (this came from Jeremy Clarkson so its open to debate lol) when the car is in neutral it goes down to idle rpm which makes then injectors fire to keep the engine turning. When coasting with the transmission engaged in gear, then the wheels keep the engine turning so you burn less fuel.

Long story short typically I downshift a few gears when on approach to traffic lights, then drop it into neutral and coast (clutch released) the final few feet to the light. Normally this means I am riding out the last few hundred rpm in 3rd, and if the light goes green I can just drop it into 2nd and be on my way (or back into 3rd with little blip if the light just went green).

I'm quoting this from another forum called Ecomodder
http://ecomodder.com/forum/showthread.php/dfco-3019.html

"How to tell if your car has DFCO

Be careful with this test as you may lose Power Steering and Power Brakes during it! Choose the right time and location to perform the test.

On any level or slightly downhill road get up to at least 40 MPH, then start engine braking by keeping the vehicle in gear and letting all the way off the throttle while keeping the clutch disengaged (MT) or keeping the transmission in a gear lower than D (AT). Notice the deceleration force and the sound of the engine.

Now tun off your ignition (This is where you may lose your PS/PB, so be wary!) and watch for any harsher deceleration or change in the pitch of the engine for a few seconds.

If nothing was any different with the ignition turned off then your vehicle uses DFCO. If it decelerated at a different rate or pitch with the ignition off then it does not use DFCO. Do not forget to start your engine back up! But, do not try to start your engine back up (with the starter motor) while the car is moving and in gear. Just putting the key on run will cause the engine to "restart" "

That last statement from that site is pure bs. ALL fuel injected cars use decel fuel cutoff. It's not only for fuel savings it's also to reduce emissions. The MAIN reason for it. It's been around even when many euro cars had the mixed electronic/mechanical KE Jetronic injection.

If you have an automatic car, shutting it down at speed can destroy the transmission by stopping all lube oil flow. (the engine turns the pump) The auto trans will also immediately unlock the torque converter AND go into neutral. It will NOT restart the engine just by turning the key back on. I have NEVER seen a car that will do this.

A manual car will in most cases change, especially on a car with drive by wire. When you coast, by design, the fuel is cut off, but the throttle is usually OPENED to reduce pumping losses and to prevent any hydrocarbon spikes in the exhaust if there's any fuel present after the injectors shut off.

Turning off the ignition will close the throttle plate immediately. However on GM vehicles, when clicking off the key, by design the throttle opens wide for a split second before it closes.

The PCM will gradually close the throttle, and you'll feel the car begin to slow.
That's why our 6 speed Accords seem to "coast" much more than you'd expect for a manual car.
The main thing that determines how much "deceleration" you'll feel when releasing the accelerator is how much the plate is actually closed, or in the case of cable throttles, is how much/fast the idle air bypass is closed.

The engine working against the closed throttle plate is what you feel as "engine braking".

Even all modern diesels (fully electronic) shut fuel off on decel. But, a diesel doesn't use a throttle plate for acceleration control as gas cars do. They for all intents and purposes have no engine braking whatsoever.

My preferred method is to shut it off and on repeatedly while coasting and if I get flames or blow the exhaust system to **** then I probably don't have fuel cut.

Even all modern diesels (fully electronic) shut fuel off on decel. But, a diesel doesn't use a throttle plate for acceleration control as gas cars do. They for all intents and purposes have no engine braking whatsoever.

But there's braking from the compression stroke right? Assuming no exhaust or jake brake.

But there's braking from the compression stroke right? Assuming no exhaust or jake brake.

There's only slight compression braking when coasting on no fuel. Most of the slowing is from high rolling resistance and poor aero in trucks. I've downshifted 6 speed F series trucks (7.3 and 6.0) and it's basically useless.

The little VW diesels don't slow very easily either, better with a manual, poor with an auto.

without the throttle plate for the engine to work against, the engine is pushed rather easily by the vehicle despite compression ratios ranging from 16:1 to 23:1. Cutting airflow to a diesel isn't good, as it will cause black smoke on reintroduction of fuel to the engine.

That's why diesels (trucks) use exhaust brakes, either the flapper type that close off the pipe or the Jacobs style which operates on the valves. There's a huge difference when you can turn them on and off when coasting. Some truck drivers won't use the service brakes till the last second when they have a jake.

There are diesels with throttle plates, some are used to enhance EGR flow, some are used, as in euro diesels for shut down to prevent the violent thump as they stop. (that's when you really notice the compression)

repeatedly shutting it on and off with a fuel injected car would take a lot of cycles to get that bang. A carbureted car though, shut it off, while pumping the accelerator, then pump the accelerator a whole bunch more then switch it back on. :naughty:

But there's braking from the compression stroke right? Assuming no exhaust or jake brake.

Wow, Fredsvt your post was right on the money! It would seem that resistance from the compression stroke would slow a vehicle but, if you think about it, following TDC you get a spring effect as the compressed air re-expands which would almost negate the resistance from the initial compression.

-Wes