Idle wear

[DrRoughneck]

There has been multiple posts about cams getting more wear at idle.

On that note, I have a question for those in the know.

You're in a traffic jam, idling in an automatic. Are you better off puting it in neutral or leaving it in drive with your foot on the break, in order to minimize cam wear?

 

[Fsharp]

I'm not in the know, but I think cam wear would be SLIGHTLY lower in neutral because idle speed is usually higher and therefore there's more oil flow and pressure. Cylinder pressure might be a little lower in neutral, without the load of the torque converter. This would make it a bit easier to open the exhaust valves, reducing the wear on the exhaust cam lobes.

 

[bullwinkle]

RPMs would be higher in neutral, allowing more oil flow, that would be better. Believe it would be a little easier on the transmission as well. Can't believe it would make a HUGE difference, though!

 

[DrRoughneck]

That's what I thought. Thanks.

 

[MobilinHyundia]

Originally Posted By: DrRoughneck
That's what I thought. Thanks.


wow, you just believe that?

 

[440Magnum]

Depends. On an old carbureted car where the idle speed drops when in gear, then you get a little more hydrodynamic wedge margin at idle.

With a modern car that idles the same speed in or out of gear, then there's no advantage in neutral as far as the cam goes (actually my 1993 car did that, so "modern" in this case can mean pretty old).

As far as the transmission, idling in gear doesn't cause any wear via slippage at all- the clutches are locked and not slipping, the torque convertor is just churning fluid and generating heat, which a healthy transmission cooler can easily keep up with. If you drop into neutral, you actually CAUSE a skosh of wear (not enough to matter, IMO) because now you're spinning clutch plates and disks against each other in their dis-engaged state, and you're shearing a little fluid in the clutch packs as well. Much more wear actually occurs when you have to put it back in gear and the clutches engage again.

As far as I can tell, its better all-around just to leave it in gear

 

[demarpaint]

Originally Posted By: 440Magnum
Depends. On an old carbureted car where the idle speed drops when in gear, then you get a little more hydrodynamic wedge margin at idle.

With a modern car that idles the same speed in or out of gear, then there's no advantage in neutral as far as the cam goes (actually my 1993 car did that, so "modern" in this case can mean pretty old).

As far as the transmission, idling in gear doesn't cause any wear via slippage at all- the clutches are locked and not slipping, the torque convertor is just churning fluid and generating heat, which a healthy transmission cooler can easily keep up with. If you drop into neutral, you actually CAUSE a skosh of wear (not enough to matter, IMO) because now you're spinning clutch plates and disks against each other in their dis-engaged state, and you're shearing a little fluid in the clutch packs as well. Much more wear actually occurs when you have to put it back in gear and the clutches engage again.

As far as I can tell, its better all-around just to leave it in gear


He pretty much nailed it. Unless you're stopped waiting a few minutes for a train there's no point in putting the car in neutral. Shifting in and out of Drive will cause more wear than just leaving the car in Drive. The cam in a late model engine will be properly lubed either way.

 

[Johnny2Bad]

Safe Driving Technique teaching is to always stop with the brake engaged and the drivetrain in gear (clutch dis-engaged if a Manual Transmission).

The idea is you are always in a position to move as quickly as possible should a vehicle (typically, a potential rear-end collision) or other moving object threaten your parked position.

If on a motorcycle, it's one foot only on the ground, foot brake on with the other foot, hand clutch dis-engaged, in first gear. Shoulder-check and mirror check immediately upon stopping.

 

[Shannow]

Originally Posted By: DrRoughneck
There has been multiple posts about cams getting more wear at idle.

On that note, I have a question for those in the know.


I haven't seen them, could you link to a handful ?

when you build a new engine, you need to hold the revs up to get help bed them in properly, but I don't recall any posts that mention more wear at idle.

 

[crazyoildude]

Some engines have cams that wear very little most can be used again sone engines like the old er 305-350 engines had issues at as low as 60,000 miles.. If you isle in N or D it slould make almost no difference. In N the cam will turn more rpm's...Ponder that thought

 

[CT8]

Most likely not worth worrying about. But then every time you go from n to d you are causing wear on the f clutch pack

 

[BrocLuno]

OK, here's the deal. If you have an older USA V-8 with a push rod valve train, the only oil that the cam lobes see is from sling off the crankshaft. There is no oil "pumped" to the lobes. This is a hold-over from the old splash oiling days.

In order to get adequate oil thrown onto the cam, the engine must be turning at 1,800 RPM or better. No problem when cruising down the freeway, as you are usually turning 2K or better.

If you have been running down the highway and then get stopped in traffic, you are fine for a while. If you are a Taxi or a Police Cruiser and you have to idle for hours, well maybe you are getting a little thin on lubrication...

When rebuilding these older style engines, there are work-arounds like scratching the lifter bore, running "direct Lube" lifters (hydraulic) or EDM Lifters (solids), all of which will bleed some oil from the lifter bore and dribble it on the cam lobes.

If you are not idling much for more than an hour at a time and/or are not running a "Hot" cam and higher rate valve springs, it's mostly a non-issue. There are a bazillion USA V-8's out there in cars and pick-ups that run fine to 300,000 miles with no special care at all.

Putting your auto-tranny in neutral and letting the idle go from 500 RPM to 750 RPM will do nothing to help. Putting it in neutral and zinging the motor to 2,500 for 30 seconds or so will replenish the sling oil on the lobes and that might help if you have one of the a fore mentioned problem Chevies with soft cam cores ...

If you have one of those, NEVER run XW-20 or any thin oil. You need HTHS and fiilm strength to combat wear ...

 

[Oldmoparguy1]

Originally Posted By: DrRoughneck
There has been multiple posts about cams getting more wear at idle.

On that note, I have a question for those in the know.

You're in a traffic jam, idling in an automatic. Are you better off puting it in neutral or leaving it in drive with your foot on the break, in order to minimize cam wear?

multiple posts in what forums? In what time frame? In all my years, I have never heard of this. Do you have a link? I would very much like to follow up on this.

 

[fdcg27]

This teaching is just plain wrong on many levels, since incompetent drivers won't be driving sticks to begin with.
I assume that the nannies teaching this "safe driving technique" have a source for free throwout bearing replacements?
Idling in neutral at rest is how any sensible person drives a stick.
Quick enough to engage first or reverse if needed and there's usually no place to go anyway.

 

[DrRoughneck]

Originally Posted By: Oldmoparguy1

multiple posts in what forums? In what time frame? In all my years, I have never heard of this. Do you have a link? I would very much like to follow up on this.


High wear because of idle:
http://www.bobistheoilguy.com/forums/ubbthreads.php/topics/3680353/fredfactory#Post3680353

Also:

http://www.bobistheoilguy.com/forums/ubbthreads.php/topics/2039371/2
" At idle, valve spring loads cause high contact stresses near peak lift, and there is not enough centrifugal force to reduce it. So the cam lobe and lifter are forced together into boundary lubrication conditions, possibly leading to metal-to-metal contact. This is why oil used to have higher concentration of ZDDP."

http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=37330
"I'm not sure when wear is the highest, but according what I have over and over heard, an engine shows generally more wear at idle (especially when cold) than when under load. Idling and revving an engine without putting load on it is especially bad for the camshaft bearings and cam lobes? "


http://www.bobistheoilguy.com/forums/ubbthreads.php/topics/2194028/Re:_Oil_Brand_doesn't_Matter_-
"Don't denigrate the test because it was done in a taxi fleet. One of the most severe tests that we do on valvetrains where I work is called the "Taxi Test". It's very simple; just run the engine at idle for 80% of the time, then do stop and go driving for 20% of the time. This is great for wiping out cams and lifters in slider-follower engines."

 

[Dyusik]

Originally Posted By: DrRoughneck
There has been multiple posts about cams getting more wear at idle.

On that note, I have a question for those in the know.

You're in a traffic jam, idling in an automatic. Are you better off puting it in neutral or leaving it in drive with your foot on the break, in order to minimize cam wear?


More can only mean the fact that there is rubbage going on when the vehicle is not in motion. More wear per mile, yes. Significant to alter engine life? Have not seen any proof.

 

[Shannow]

Originally Posted By: DrRoughneck
Originally Posted By: Oldmoparguy1

multiple posts in what forums? In what time frame? In all my years, I have never heard of this. Do you have a link? I would very much like to follow up on this.


High wear because of idle:
http://www.bobistheoilguy.com/forums/ubbthreads.php/topics/3680353/fredfactory#Post3680353

Also:

http://www.bobistheoilguy.com/forums/ubbthreads.php/topics/2039371/2
" At idle, valve spring loads cause high contact stresses near peak lift, and there is not enough centrifugal force to reduce it. So the cam lobe and lifter are forced together into boundary lubrication conditions, possibly leading to metal-to-metal contact. This is why oil used to have higher concentration of ZDDP."

http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=37330
"I'm not sure when wear is the highest, but according what I have over and over heard, an engine shows generally more wear at idle (especially when cold) than when under load. Idling and revving an engine without putting load on it is especially bad for the camshaft bearings and cam lobes? "


http://www.bobistheoilguy.com/forums/ubbthreads.php/topics/2194028/Re:_Oil_Brand_doesn't_Matter_-
"Don't denigrate the test because it was done in a taxi fleet. One of the most severe tests that we do on valvetrains where I work is called the "Taxi Test". It's very simple; just run the engine at idle for 80% of the time, then do stop and go driving for 20% of the time. This is great for wiping out cams and lifters in slider-follower engines."


You're using one of my posts that's expressly about warm-up, another that is expressly about warmup...they are NOT about your topic, or statement to that effect.

 

[15SilvyEcotec]

My 5.3 L83 idles at 500 RPM's in gear or in neutral when warm. Also my oil pressure is 40 PSI at idle to 3,700 RPM's then goes to 70 PSI from there to 5,600 RPM's when the duel pressure pump goes to the high side if that matters?

 

[SteveSRT8]

Like 440 said, any modern engine has no problem idling for years if all is correct.

We used to sit and figure plans in Dodge 318's for hours at idle, they never skipped a beat. Same in our Silverado delivery trucks. Our fleet vans run all day sometimes at 1500 or 1750 and last 250k to 500k miles.

Complete non issue in most vehicles...

 

[demarpaint]

Originally Posted By: DrRoughneck
There has been multiple posts about cams getting more wear at idle.

On that note, I have a question for those in the know.

You're in a traffic jam, idling in an automatic. Are you better off puting it in neutral or leaving it in drive with your foot on the break, in order to minimize cam wear?


How about shutting it off? Zero wear occurs when an engine is off. My stick shift van is always in N when idling, and my A/T vehicles idle at the same speed in N or D so idling in N or D makes no difference.

My only concern with shut down vs. idle, is starter wear when restarting, and is there a tiny spike in wear restarting an engine? I'd think leaving it on in D would be the best bet. Opinions will vary.