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What causes sludge? #1079968 02/05/08 08:06 PM
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glennc Offline OP
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What conditions lead to sludge being formed, and how does it actually occur, chemically? Why are some engine designs particularly prone to it and others relatively immune? (What is actually different in the motor)? What motor oil characteristics are most important in resisting its formation?

Re: What causes sludge? [Re: glennc] #1079973 02/05/08 08:12 PM
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MolaKule Offline
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The value of a scientific theory is its ability to prompt further study, not that it has any relation to the established facts of scientific reality.
Re: What causes sludge? [Re: MolaKule] #1080056 02/05/08 09:56 PM
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GROUCHO MARX Offline
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A flight back in time on that thread!


80% of people polled say that their neighbor should take mass transit to work.
Re: What causes sludge? [Re: GROUCHO MARX] #1080095 02/05/08 10:37 PM
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02zx9r Offline
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good info thanks

Re: What causes sludge? [Re: 02zx9r] #1080150 02/06/08 12:10 AM
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deven Offline
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 Originally Posted By: 02zx9r
good info thanks


+2


Proud user of ROYAL PURPLE products!

2019 BMW 330i X-drive(Factory Fill)

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Re: What causes sludge? [Re: glennc] #1080433 02/06/08 12:41 PM
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Bamaro Offline
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Interesting thing from the link above is :
1. Promoted by mixed driving conditions in which there is stop and go and highway operations.

I would think that highway driving would have the opposite effect.


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Re: What causes sludge? [Re: Bamaro] #1080436 02/06/08 12:46 PM
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deven Offline
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 Originally Posted By: Bamaro
Interesting thing from the link above is :
1. Promoted by mixed driving conditions in which there is stop and go and highway operations.

I would think that highway driving would have the opposite effect.


Its a MIXED condition that leads to sludge. It causes temp fluctuation and oxidation can take place.


Proud user of ROYAL PURPLE products!

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KEEP IT SIMPLE STUPID. IT'S ONLY OIL
Re: What causes sludge? [Re: Bamaro] #1080542 02/06/08 02:53 PM
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Dyoel182 Offline
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 Originally Posted By: Bamaro


I would think that highway driving would have the opposite effect.


The highway mileage does have the opposite effect since the oil is at full temp for a while.

Re: What causes sludge? [Re: Dyoel182] #1080552 02/06/08 03:01 PM
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glennc Offline OP
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MolaKule I appreciate the link you provided. Some things I still don't understand, though.

Other than being an inky black substance, etc, what exactly is it? Why is the oil not able to hold it in suspension? I thought that was a big part of what oils were supposed to have additives for.

Why does low crankcase temp contribute to it? Is it primarily because at low temps the chemical action of the oil to break it down and dissolve or suspend it is not sufficiently strong? What oil characteristics help with that?

Why does it occur when there are high combustion temps?

Why does it occur when you have lean burning?

Still trying to understand it more fundamentally.

Thanks again for the earlier reply.

Re: What causes sludge? [Re: glennc] #1080624 02/06/08 04:32 PM
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ARB1977 Offline
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[censored] design and neglect.


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Re: What causes sludge? [Re: ARB1977] #1080642 02/06/08 05:01 PM
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JAG Offline
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Here are some articles in the link below, Glenn. http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=900993&fpart=1

I think I have posted more links on the forums on this subject than what's in that thread if you care to search for them.

MolaKule or Bruce or anyone, correct me if I'm wrong anywhere below.

My answer to the lean burn question is that it increases the nitrous oxides and that increases the nitration of the motor oil which is a major cause of oil degradation. Lean burn also causes high combustion temps which will further degrade the oil in the ring belt (which is already well above bulk oil temp).

High combustion temps increases the reaction rate of the degradation reactions. Rule of thumb is that a reaction rate doubles for every 10C increase. Arrhenius Equation: http://en.wikipedia.org/wiki/Arrhenius%27_law

Detergents and dispersants are similar and there is some overlap of capabilities but generally common modern motor oil dispersants are better at keeping 'nasties' in suspension at low temperatures and detergents are better at it at high temperatures. Metallic-based detergents do the bulk of acid neutralizing and dispersants can do it but less so.

I'll pass on the other questions, at least for now. :)

One more link and it's a shame the pics have been taken down. Maybe they can be found through detective work. If not, the discussion is still good. http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=803291#Post803291

Re: What causes sludge? [Re: ARB1977] #1080643 02/06/08 05:01 PM
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mechtech2 Offline
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Usually a bad PCV system.

Re: What causes sludge? [Re: mechtech2] #1080663 02/06/08 05:29 PM
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Dyoel182 Offline
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You mean a faulty design PCV system?

Re: What causes sludge? [Re: Dyoel182] #1080677 02/06/08 05:46 PM
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ekpolk Offline
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 Originally Posted By: Dyoel182
You mean a faulty design PCV system?
It could be that, or a good one that's become gummed up, or is otherwise not functioning properly.


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Re: What causes sludge? [Re: deven] #1080777 02/06/08 08:24 PM
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02zx9r Offline
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 Quote:


I would think that highway driving would have the opposite effect.


Its a MIXED condition that leads to sludge. It causes temp fluctuation and oxidation can take place. [/quote]

even if you get on the highway and get the motor/oil up to optimum temps and stay at that temp for sustained time/distance so condensation and fuel burn off??

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