Looks like sludge/engine black death just won't go away!!!
http://www.wynnsnz.co.nz/show-news.php?id=23
The solution.........use 100% percent PAO Group IV/V synthetic.........or use cheap oil.........then get sludge...........and then flush it out(maybe), with expensive and harmful chemicals.
I say it's better to avoid it in the first place!
This is a quote......
Performance
[edit] Advantages
The technical advantages of synthetic motor oils include:[citation needed]
* Measurably better low and high temperature viscosity performance
* Better chemical & shear stability
* Decreased evaporative loss
* Resistance to oxidation, thermal breakdown and oil sludge problems
* Extended drain intervals with the environmental benefit of less oil waste.
* Improved fuel economy in certain engine configurations.
* Better lubrication on cold starts
* Longer engine life