Detergents! Do they clean?

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BigShug681

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Do the detergents in oil actually clean? Hopefully this will bring about some good discussions
 
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I would say detergents clean. Here is what my Santa Fe looked like at 300K miles when the camshaft snapped. It was run its whole life on quality synthetics.

[Linked Image]
 
I believe we are discussing two different things:

1. Keeping things clean; preventing deposits, varnish, build-up....etc
2. Cleaning up an existing mess. Removing varnish, sludge....etc.

#1 is what detergents are generally regarded as doing. #2 is quite a bit more difficult and one will likely observe very little progress in this department with your typical engine oil.
 
Originally Posted by BigShug681
Originally Posted by SonofJoe
Always good to get both sides of the story...

https://www.bobistheoilguy.com/foru...ergents-magnesium-vs-calcium#Post4879933

I find it interesting that you say they don't clean, would you care to explain how engine oil gets dirty if it's not actively cleaning? I know there are many factors to the dirtying of oil but I also believe cleansing is one of them


If you're asking, why do engine oils go from a nice, clear straw colour to an opaque black, that's easy. Take an oil. Put it in a glass cylinder. Put it in an oven & heat it up & bubble air through it for a few days. Before you know it, the oil will be black. What you're witnessing is the base oil oxidising. Oxygen is finding weak points in the base oil chemical structure (usually benzylic hydrogen sites), opening them up and initiating a chain reaction which leads to the formation of complex organic acids.

You should note from this that you DON'T need oil to be actually inside a combustion engine & exposed to blow-by gas & all its associated nasties to turn black. Air, heat & time are all you need. However if you do put oil in an engine & run it, the rate at which the oil oxidises increases markedly. This is because things like the presence of wear metals, NOx & partially burnt fuel all act as oxidation catalysts.

You can slow down the rate of oxidation by a variety of means. ZDDP (Zinc) is an excellent antioxidant as are Diphenylamines, Phenolics, etc. Overbased Metallic Detergents are sort of a poor man's antioxidant. Their job is to neutralise acids as they're formed and stop them further catalysing oxidation. The active ingredient in something like 300 TBN Calcium Sulphonate is not the Calcium Alkyl Benzene Sulphonate 'detergent' but the alkaline Calcium Carbonate & Calcium Hydroxide that the detergent molecules maintain in colloidal suspension.

Oh, and one shouldn't forget the other thing that detergent do is preventing rust inside your engine.

Hope that helps...
 
Originally Posted by SonofJoe
... Hope that helps...
Yes, excellent explanation. Thanks!

In my Mazda's long life, I noticed some brands of conventional 10W-40 seemed to form what I would call sludge (the gray clay-like stuff), while other brands apparently made it vanish. Did not see any of this goo after about 2003, so it spent its last few years looking as clean under the valve cover as StevieC's engine.
 
I think that is related to certain oils being able to deal with extra moisture in the crankcase that the PCV / Breather is not adequately eliminating and that the oil holds onto rather than boiling off. We have a Toyota Corolla in the family that we were convinced had a coolant leak into the oil because at 5K it would come out with clay coloured oil. We did the pressure test, measured the coolant in the overflow bottle and none was used. Even over 2 OCI's. We changed the oil to another brand and the problem went away. The internals of the engine were clean under the valve cover just the oil would come out an odd colour.

Although this engine was not short-tripped frequently I have seen similar in engines that are. Primarily VW's from the 1980's / Early 1990's.

Hope that experience helps.
 
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Originally Posted by OVERKILL
I believe we are discussing two different things:

1. Keeping things clean; preventing deposits, varnish, build-up....etc
2. Cleaning up an existing mess. Removing varnish, sludge....etc.

#1 is what detergents are generally regarded as doing. #2 is quite a bit more difficult and one will likely observe very little progress in this department with your typical engine oil.


+1
We aren't talking about laundry detergent here. The primary function of detergents in oil is to keep things clean by holding contaminants in suspension.
 
Last edited:
Originally Posted by OVERKILL
I believe we are discussing two different things:

1. Keeping things clean; preventing deposits, varnish, build-up....etc
2. Cleaning up an existing mess. Removing varnish, sludge....etc.

#1 is what detergents are generally regarded as doing. #2 is quite a bit more difficult and one will likely observe very little progress in this department with your typical engine oil.


Exactly. Detergents exist to keep the oil clean, not the engine.
 
Originally Posted by StevieC
I think that is related to certain oils being able to deal with extra moisture in the crankcase that the PCV / Breather is not adequately eliminating and that the oil holds onto rather than boiling off. We have a Toyota Corolla ... that we were convinced had a coolant leak into the oil because at 5K it would come out with clay coloured oil. ...
I believe you're talking about a different phenomenon. I did not see "clay-coloured oil," but instead gray sediment in low spots on the cylinder head, and maybe in drained oil. I always tried to minimize short trips, and never saw moisture in it.

The old Chevrolet in my signature below always had similar-looking of gray gunk in the oil filter housing when we changed the filter.
 
I was intrigued by this 'clay coloured' oil.

I don't know if this is relevant but if you take any neat overbased metallic detergent and high shear mix it with some water, it goes from a beautiful, clear & bright dark brown liquid to an opaque milky coffee coloured goo.

I'm not sufficiently up with colloidal chemistry to say what exactly is happening but I'd hazard a guess that the water is disrupting the colloidal miscelle structures (the tiny blobs of chalk surrounded by polar detergent molecules) such that free Calcium Carbonate is being first being liberated and then agglomerating.

You said 'clay' but maybe what you were seeing was chalk?


Oh, and if you did have a coolant leak, the water would contain glycol making it more polar & more likely to interact with the micelles.
 
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Originally Posted by CR94
Originally Posted by StevieC
I think that is related to certain oils being able to deal with extra moisture in the crankcase that the PCV / Breather is not adequately eliminating and that the oil holds onto rather than boiling off. We have a Toyota Corolla ... that we were convinced had a coolant leak into the oil because at 5K it would come out with clay coloured oil. ...
I believe you're talking about a different phenomenon. I did not see "clay-coloured oil," but instead gray sediment in low spots on the cylinder head, and maybe in drained oil. I always tried to minimize short trips, and never saw moisture in it.

The old Chevrolet in my signature below always had similar-looking of gray gunk in the oil filter housing when we changed the filter.


I don't really know what it is, I was just guessing what I thought. The oil brand seemed to fix the problem so maybe a different add-pack can fix the problem. I don't know. It was certainly before BITOG and was with oils far less superior than today's standards.
 
Originally Posted by StevieC
I would say detergents clean. Here is what my Santa Fe looked like at 300K miles when the camshaft snapped. It was run its whole life on quality synthetics.

[Linked Image]


Still looks new inside! Too bad it died on ya.
 
Originally Posted by SonofJoe
Originally Posted by BigShug681
Originally Posted by SonofJoe
Always good to get both sides of the story...

https://www.bobistheoilguy.com/foru...ergents-magnesium-vs-calcium#Post4879933

I find it interesting that you say they don't clean, would you care to explain how engine oil gets dirty if it's not actively cleaning? I know there are many factors to the dirtying of oil but I also believe cleansing is one of them


If you're asking, why do engine oils go from a nice, clear straw colour to an opaque black, that's easy. Take an oil. Put it in a glass cylinder. Put it in an oven & heat it up & bubble air through it for a few days. Before you know it, the oil will be black. What you're witnessing is the base oil oxidising. Oxygen is finding weak points in the base oil chemical structure (usually benzylic hydrogen sites), opening them up and initiating a chain reaction which leads to the formation of complex organic acids.

You should note from this that you DON'T need oil to be actually inside a combustion engine & exposed to blow-by gas & all its associated nasties to turn black. Air, heat & time are all you need. However if you do put oil in an engine & run it, the rate at which the oil oxidises increases markedly. This is because things like the presence of wear metals, NOx & partially burnt fuel all act as oxidation catalysts.

You can slow down the rate of oxidation by a variety of means. ZDDP (Zinc) is an excellent antioxidant as are Diphenylamines, Phenolics, etc. Overbased Metallic Detergents are sort of a poor man's antioxidant. Their job is to neutralise acids as they're formed and stop them further catalysing oxidation. The active ingredient in something like 300 TBN Calcium Sulphonate is not the Calcium Alkyl Benzene Sulphonate 'detergent' but the alkaline Calcium Carbonate & Calcium Hydroxide that the detergent molecules maintain in colloidal suspension.

Oh, and one shouldn't forget the other thing that detergent do is preventing rust inside your engine.

Hope that helps...

Very interesting then how do companies get away with saying said oil cleans better than said oil?
 
Had figured an oil that turns dark faster is doing its cleaning - suspend some contaminates. Goes a lot of miles and stay clean, not so much.
 
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