Black Sludge Formation

[MolaKule]

Just studied a paper regarding Sludge Formation and thought I would share certain
highlights with you:

A. Black Sludge is defined as thick to solid material with low water content, of dark color, light oil insolubles,
and typically found in rocker cover, cylinder head, timing chain cover, oil sump, oil pump screen, and oil rings in variable quantities.

B. Cause of Black Sludge in more modern engines.
1. Promoted by mixed driving conditions in which there is stop and go and highway operations.
2. Starts with Nitrous oxides in Lean-Burn engines reacting with blow-by gasses.
3. High spark advance, high temperature of combustion, lean fuel/air ratios, high compression.
4. Fouled air ventilation systems (PCV), combined with low operating temperature driving conditions.
5. Longer oil change intervals.
6. Higher oil temperatures.
7. Lower sump capacity.

 

[jjbula]

In the beginning......My journey to this board started after I received a letter from toyota on sludge problems in my Camry.

Thats why I've been interested in low Noack oils. Since then I've learned low Noack is just one facet of the oil.

Perhaps Auto-Rx, high quality oil (not necessarily with the lowest Noack), and reasonable oil change intervals (backed up with analysis) can keep the sludge at bay.

I'm also starting to like the idea of 2 oz. of Auto-Rx every oil change to keep possible sludge away.

Right now I change the oil too often because dark oil is 'worrisome' to me.
Where does the VI go when it 'shears away'?
Does a pour point deppressant wear out and contribute to sludge?

I seem to be turning to oils with close numbers, 10w30 and 15w40, as good candidates for a near sludge free oil.

Thoughts on Camry's or Sludge control?

[ August 04, 2002, 10:51 PM: Message edited by: jjbula ]

 

[MolaKule]

jjbula,
"Perhaps Auto-Rx, high quality oil (not necessarily with the lowest Noack), and reasonable oil change intervals (backed up with analysis) can keep the sludge at bay."

I think oil changes (as indicated by analysis) will keep most of the sludge at bay.

"Right now I change the oil too often because dark oil is 'worrisome' to me."
Dark oil indicates that "stuff" is in suspension.

"Where does the VI go when it 'shears away'?
Does a pour point deppressant wear out and contribute to sludge?"

Many VII's are also used for the PourPoint depressant. Yes, the polymers that become sheared have to go into the oil and oxidize along with the rest of the crud resulting in sludge.

 

[jjbula]

Thanks,

I think I may extend drain intervals yet.

Perhaps a good look under the cam cover every once in a while will give me the confidence to follow through.

 

[jjbula]

Not expecting an answer on such nit-picky question but.....

Are there different qualities of VII's being used today?

I've heard VIIs havet improved and would like to avoid the oils with the older type VII's.

I suspect only the bottom of the barrel oils use VII's of lesser quality.

 

[joee12]

"I seem to be turning to oils with close numbers, 10w30 and 15w40, as good candidates for a near sludge free oil."

With that said, what brand of oils are you trying? -Joe

 

[jjbula]

Currently running Valvoline Synpower 10w30.

Chose it for a readily available spec sheet on the internet and low Noack - 8

Nowadays I believe a Noack of less than 15 (the SL standard) is good enough. The are better indications of what makes an oil high quality. I will probably use Auto-Rx every 3 to 4 oil changes.

The cost of Auto-Rx will be mitigated by longer drain intervals with a high quality oil.

I want to use an oil with at least some PAO in it.

Schaeffer Blend, Amsoil, Redline, M1, Delvac, and Chevron Synth seem to be the best candidates. Have not made any firm decisions yet.

 

[Patman]

quote:

---

Originally posted by jjbula:
Currently running Valvoline Synpower 10w30.

Chose it for a readily available spec sheet on the internet and low Noack - 8

Nowadays I believe a Noack of less than 15 (the SL standard) is good enough. The are better indications of what makes an oil high quality. I will probably use Auto-Rx every 3 to 4 oil changes.

---

How often will these be then? Auto-rx is good but I don't think it needs to get the full
treatment all that often. Once the engine is cleaned and you use a good oil, it won't get
dirty again for quite a while. I think I'll probably do the Auto-rx full treatment only once every
50-60k.

 

[jjbula]

I plan on doing analysis and, hopefully, extend drains to 6-8K or 6 months.

May go 12 months (don't put miles on that fast) and only change filter at 6 months.

If I change more often I will definitely use Auto-Rx less frequently.