Is Sludge Rare?

[ZZman]

Out of all the vehciles on the road today you only hear of a few motor designs that were sludge prone. Many if not most cars have varnish and that seems to be a fairly normal occurrence.

My question is do you think many cars while not a "sludge motor" have some amount of sludge or deposit build up in the valvetrain or other areas? Would it be because of oil choice? Too long OCI's? Engine issues? Or is this just a very rare thing to have period?

 

[JAG]

I often ask people that I know if I can take off their engines' oil fill cap and pull the dipstick to "take a look". I often find hard crusty deposits and varnish. So far I see that more often than not.

So what I see is that it's not uncommon. All it takes is to push the oil too far. How far is too far is dependent on the specific circumstances (engine type, engine "tune", driving habits, oil choice, oil change interval, weather, etc.).

 

[mechtech2]

It sure is getting more rare to see heavy internal engine deposits.
Better and tighter designs, with more precise engine controls [fuel and spark] all help .
A sure way to get sludge is to have a bad PCV system, and neglect changing your oil.
That over rides any and all good modern design features.

 

[BrianWC]

I would suspect it's not as rare as believed given all that can happen to an engine over today's extended oil drain intervals. A stuck PCV valve, coolant contamination, running low on oil.... There's a lot that can happen when someone only removes an oil cap every 7-10k miles....

That's no knock on extended intervals. But I think manufacturers are trying to push a low maintenance experience on customers. Therefore, the customer doesn't believe he/she has an reason to worry about their oil condition until that OLM light comes on.....

 

[jldcol]

May have to define your term here a little. Almost all engine will get some kind of deposits, commonly varnish-like baked on stuff along with some carbon/soot buildups. I define sludge as that oily-jelly, that's somewhat sticky, enough to cling to surfaces, even those inpinged by some oil flow. This stuff really won't dissolve in oil all that well, so hard to get out of engine. Piston crowns,and rings/grooves will always carbon up to some extent, unlees you have enough oil getting into cylinder to clean off, although to much oil in combustion will cause other problems/deposits. Valve head/stems also deposits, primarily from gas additives.