Does oil get thicker as it ages?

[AnarchyX]

Just wondering because if the oil is containing "trapping" dirt, wouldn't that mean that the dirtier it gets the "thicker" the oil gets?

just thought I'd throw something new into the mix, especially since it's something that makes sense, but hasn't been discussed as far as I know.

 

[Quattro Pete]

If you look at all the UOAs that have been posted on BITOG, you will notice that most oils in most applications will initially get thinner as VIIs break down. Then, as miles keep piling on (say above 10K), most oils begin to thicken up.

 

[Artem]

^That plus some fuel dilution and slight shearing from use (esp if the engine is hard on the oil) which is what makes it thin down some.

Of course the oil gets thicker with age because it's loading up more and more with all the [censored] it collects and cleans. It only gets serious if the oil gets low on TBN and so those acids aren't neutralized and so dirt starts to build up FAST and the oil thickens.

 

[dparm]

Oxidation causes thickening. In diesels, "soot loading" does.

If the car saw repeated high-temperatures it will thicken as well.

 

[Rand]

A good oil will thin slightly then thicken slightly.

poorer quality oils will usually thin out of grade then thicken to 2-3x the viscosity of the virgin oil.

 

[mechtech2]

Anarchy -
Like the guys said, it may shear thin a bit, then after long use thicken. This is the normal expectation.

But your question about dirt thickening it is something else. It would have to make it more dense, but not actually help with any oil properties.
Gas dilution would of course make it thinner.

 

[A_Harman]

Originally Posted By: dparm
Oxidation causes thickening. In diesels, "soot loading" does.

If the car saw repeated high-temperatures it will thicken as well.


^ What he said!