engine braking leading to oil consumption?

[Craig in Canada]

It's not the engine braking that's causing oil consumption, per se, it is the persistent condition of high vacuum caused by running with the throttle closed at "high" RPM. My first thoughts on this are PCV, or valve stem seals. Obviously the former is cheaper and easier.

I think this is several threads now you've been advised to change or check the PCV for multiple reasons - I'd do it.

 

[oilyriser]

Originally Posted By: gathermewool
Engine braking is fine. You'll produce zero extra wear if all you're doing is keeping it in gear to slow you down. You'll only wear out your clutch if you downshift and let out the clutch at a much lower RPM than needed for the speed you're at. If you really want to engine brake by downshifting, then clutch in and blip the throttle to the RPM consistent with the speed you're at as you clutch in. There's very little wear if the clutch and flywheel engage at just about the same RPM.


You use the clutch when shifting gears? How quaint.

With lots of practice (and luck) you can do a clean shift only using your right foot and one hand. I don't quite have enough practice...

 

[Mr_Incredible]

DFCO (deceleration fuel cutoff)is a good reason to engine brake. When you let off the gas and coast (without pulling it out of gear) many vehicles shut off the fuel at certain rpm ranges. I see it using my ScanGaugeII on my truck, the Camaro, and Wife's Prius.

My last tank in my '89 CRX was a DFCO test and it used a lot of oil doing it. I'm trying coasting out of gear on this tank. The oil level is staying where it was.

 

[Bryanccfshr]

Originally Posted By: rationull
Originally Posted By: Bryanccfshr

If you ask me pulling a clutch and replacing it is easier than doing 4 disc brakes.



I think that rather depends on the car


Oh, it Doesn't apply to most "cars" Especially those transversely mounted FWD ones . I don't own any of those.

 

[Jim 5]

Originally Posted By: oilyriser
Originally Posted By: gathermewool
Engine braking is fine. You'll produce zero extra wear if all you're doing is keeping it in gear to slow you down. You'll only wear out your clutch if you downshift and let out the clutch at a much lower RPM than needed for the speed you're at. If you really want to engine brake by downshifting, then clutch in and blip the throttle to the RPM consistent with the speed you're at as you clutch in. There's very little wear if the clutch and flywheel engage at just about the same RPM.


You use the clutch when shifting gears? How quaint.

With lots of practice (and luck) you can do a clean shift only using your right foot and one hand. I don't quite have enough practice...


It's easier on a motorcycle. I don't need my clutch there except for 1st gear and BIG downshifts. In a car, the shift throw isn't a 1/2" like on a bike, it's sometimes 10" or more. I haven't had the courage to try this on any of my own vehicles. I'll pop it out of 4th or 5th into neutral though.

 

[Dieselbob]

I have ALWAYS coasted down in high gear until right before the car bucks, and then kick the transmission into neutral without using the clutch and then lightly apply apply the brakes to stop. I've been doing that since I got my license in 1984, and I haven't wrecked an engine or replaced a clutch yet.

 

[ADFD1]

I pretty much do the same thing, makes stopping a lot easier. Clutch braking causes issues.

AD

 

[Jim 5]

Originally Posted By: Dieselbob
I have ALWAYS coasted down in high gear until right before the car bucks, and then kick the transmission into neutral without using the clutch and then lightly apply apply the brakes to stop. I've been doing that since I got my license in 1984, and I haven't wrecked an engine or replaced a clutch yet.


Not to mention that on a modern fuel injected car, this approach shuts the fuel injectors off (based on my instant fuel economy readout). Coasting in neutral doesn't. Might get an extra .01 MPG this way.

 

[Mr_Incredible]

Coasting in neutral can often be better than DFCO.

Coasting in gear drops speed faster than coasting in neutral when working against engine compression. The downhill section would have to be pretty steep to keep speed up.

Some places where I coast can last for several to many times farther than I could go with DFCO.

Much better than .01mpg, IMO.

 

[Gary Allan]

We're really dealing with engine vacuum. Diesels compress many CFM of air ..they don't have a throttle to produce vacuum.

..but that said, I really think the notion of engine braking causing excess wear, outside of something like an older gasoline school bus ..where the mass you're moving can potentially "over wind" the engine ..sending the rods flaying off into the nether world (which would bee termed "damage") is just not apparent.

I can't see where excessive vacuum would have any more (or even as much) impact than excessive cylinder pressure on the other end of the equation. One has to concede that you can't go perpetually down hill.

..and yes, your PCM, depending on various inputs and based on its "fuel strategy", will shut fuel off when coasting above idle. I imagine if you were descending from 8000 ft, and were taking your time, that the coolant temp may retreat to a point where the PCM provided fuel where none was needed otherwise.

 

[Colt45ws]

Originally Posted By: oilyriser
Originally Posted By: gathermewool
Engine braking is fine. You'll produce zero extra wear if all you're doing is keeping it in gear to slow you down. You'll only wear out your clutch if you downshift and let out the clutch at a much lower RPM than needed for the speed you're at. If you really want to engine brake by downshifting, then clutch in and blip the throttle to the RPM consistent with the speed you're at as you clutch in. There's very little wear if the clutch and flywheel engage at just about the same RPM.


You use the clutch when shifting gears? How quaint.

With lots of practice (and luck) you can do a clean shift only using your right foot and one hand. I don't quite have enough practice...

Ive done this in my Moms car going 4th->5th. Lightly push against the shifter, let off the gas, and it pops right out. Move over to 5th and hold it lightly against the gate. When it hits the correct RPM it falls in.

 

[ADFD1]

I'd be a little concerned about the syncros (sp), upshifting and downshifting, popping into Neutral is fairly easy at the right speed. I found Honda Civics very easy to shift w/o the clutch, but would be concerned in cars that weren't so easy. Best to use the clutch in cars.

AD

 

[Colt45ws]

I know. Ive only done it once or twice, thats the thing Im concerned about. However, I was using very light pressure so I doubt it did anything.

 

[Jim 5]

I do it on the bike all the time and I've had a typical cassette style motorcycle transmission apart and have repaired it. When you have a cassette style transmission apart, you can see why it works and how unloading the the side of each gear's dogs from the adjacent gear's window permits a seamless shift.

Applying a slight pressure on the shift fork while unloading (taking engine load away - no acceleration or deceleration)the gears can permit the gear to disengage and re-engage without any wear in either case.

On a bike it's really easy. While accelerating moderately to hard apply upward pressure on the shift lever when you are ready to shift, chop the throttle for a quarter second and the gear shift will just happen, then you're back on the gas. It happens all at once. Many people with bikes that have hard (not gentle/soft) rev-limiters just apply upward pressure on the shifter and let the engine bounce off the rev-limiter, when this happens, it's enough to unload the gears long enough and the shift just happens.

Downshifting on a bike is just the reverse. On a car it's got to be harder because the thow is longer and unlike a bike you have to pass through neutral along the way.

 

[Gary Allan]

Anybody who knows how to double clutch and shift without using it. I had a clutch cable snap in Camp Hill, PA and drove over 250 miles without a clutch. I think it would be more difficult now with fuel injection. There I was able to start the thing in gear floored. Shifting was not rocket science.

 

[Popinski]

seriously.. on common roads.. it's easier to pop in neutral, let it coast and use a little bit of brake to stop. Engine braking is useless and unnecessary wear.

I think people engine brake because:

A. they watch too many race car videos on youtube

B. Watched Fast and the Furious movies.

C. People just think it's cool because of the sound of the engine and exhaust.


Unless of course you are in a very hilly/mountainous roads, then it's understandable.

 

[KrisZ]

Originally Posted By: Popinski
seriously.. on common roads.. it's easier to pop in neutral, let it coast and use a little bit of brake to stop. Engine braking is useless and unnecessary wear.

I think people engine brake because:

A. they watch too many race car videos on youtube

B. Watched Fast and the Furious movies.

C. People just think it's cool because of the sound of the engine and exhaust.


Unless of course you are in a very hilly/mountainous roads, then it's understandable.



Oh, really, well last time I checked, the mnual transmission was in use long before video games, TV and movied were invented, and back in those days you had to rev. match on the upshifts and downshifts, so your nice little theory doesn't hold water unless you talk to some 17-year olds. These practices were developed to reduce the wear and tear on the drive train, the invention of synchronizers eliminated the need to rev. match and double clutch to an extent. It is still a good practice to double clutch and rev. match, as it puts less strain on the synchros, especially at higher RPM's.

While downshifting is not necessery, it puts zero wear on the drivtrain compared to power shifting at redline, or simply starting up the hill.

So please get your facts strait.

 

[FZ1]

I think "strait" is spelled straight,isn't it?

 

[7777]

Originally Posted By: FZ1
False economy. Wasteing your motor to save your brakes. Don't engine brake.


Before you start correcting other people's spelling,try correcting yours first.
(wasteing/wasting)See,nobody is perfect,including you.He got his point across, thats all that matters.

 

[Gary Allan]

Quote:
Engine braking is useless and unnecessary wear.


What wear? I've never heard of any "wear" associated with engine braking.

Seriously (it's hard for me to not sound like a wise guy) ..just when has any engine/trans died from normal downshifting and engine braking? It's what you do with a manual trans. It's been in many owners manuals (haven't checked lately).