Carbon - Soot

[WyrTwister]

Most of us have read the reason oil in diesel engines quickly turns dark / black is from soot .

I have also read the soot is abrasive . However graphite is sometimes used as a lubricant . Can some one please explain the difference ?

Also , is the soot to " fine " to be captured / trapped by the oil filter ?

Also , this is / may be applicable , to a much smaller degree in gasoline engines .

Thanks ,

 

[Boomer]

One reason can be the structure of the carbon. Graphite, a lubricating form of carbon, is plate like in structure due to the nature of the double bonds between the carbon atoms. Regular carbon (ie a soot particle) has mainly all single bonds and can be hard and angular. Remember that a diamond is very pure carbon in this state with no impurities and we all know how hard diamonds are.

 

[kschachn]

Originally Posted by Boomer
One reason can be the structure of the carbon. Graphite, a lubricating form of carbon, is plate like in structure due to the nature of the double bonds between the carbon atoms. Regular carbon (ie a soot particle) has mainly all single bonds and can be hard and angular. Remember that a diamond is very pure carbon in this state with no impurities and we all know how hard diamonds are.

Right, but the hardness of diamond isn't really related to the purity, it is because of the three-dimensional structure of four covalent bonds between each atom. Graphite would essentially be quite strong in the plane if you could stress it like that.

 

[sdowney717]

Soot is not abrasive unless it gets bigger, as long as its 1/10 micron its ok and has not been allowed to clump together by depleted oil additives. Otherwise diesel engines would completely wear out fast as they make a lot of soot. Soot is really small, too small to easily filter out from oil. I dont like unrestrained soot in my oil so I added a roll of toilet paper filter to my Dodge ram diesel 2005 truck. I started that thread in the bypass filter section. Even that TP will not remove small soot particles, but it will help.

 

[WyrTwister]

Correct or not . I do not know .

But I once read that particles smaller than a certain size , do not hurt in engine oil ? It said it acts as a " polish " ?

 

[oil_film_movies]

Organic chemistry. example: All carbon are the buckyballs, a form of carbon that is made up of 60 atoms and shaped like a hollow soccer ball. Carbon molecules can get really weird, with special shapes, kind of like constructing them out of Tinker Toys, ya know?

 

[UberArchetype]

Originally Posted by sdowney717
...I added a roll of toilet paper filter to my Dodge ram diesel 2005 truck.

Better filtration is one way to avoid accelerated diesel engine wear. High-density depth filters, centrifuges and gravity are the only 3 ways I am aware of to remove soot from engine oil. The oil itself and the oil change cycle is typically the only thing protecting a diesel from soot-induced wear. If you are relying only on oil changes, I would recommend establishing a baseline OCI schedule with oil analysis to determine where your soot red zone is. Typically short OCIs with a good quality diesel-rated lube will be worry-free in most consumer applications. Severe service (towing, etc.) might be another story.

 

[Triple_Se7en]

Originally Posted by sdowney717
...........oil so I added a roll of toilet paper filter to my Dodge ram diesel 2005 truck. I started that thread in the bypass filter section. Even that TP will not remove small soot particles, but it will help.


I'll bet it was Charmin 3-4-ply and not Scotts 1000 one-ply.

 

[oil_film_movies]

Both Gasoline Direct Injection engines and of course Diesel engines produce soot in the oil.
"Soot reduces the effectiveness of anti-wear additives and its effect on wear depends upon the characteristics of the particles and agglomerates of soot. Abrasive wear occurs and wear scar width closely matches the primary particle size. Oil thickening was found to enhance timing chain elongation due to abrasive action of soot on pins and bushing."
---- https://www.sciencedirect.com/science/article/pii/S0301679X15000432

 

[UberArchetype]

Originally Posted by oil_film_movies
Both Gasoline Direct Injection engines and of course Diesel engines produce soot in the oil.

True. But diesels put an order of magnitude greater amount of it in the oil - even more if tuned hot.