What causes oil to thicken

[Fireturk41]

I have a CAT 3208 T non aftercooled in a boat. I use rotella 15-40. This last analysis showed the oil thickened to 50wt with no signs of coolant or water in it. Also stated contamination was normal. Potassium was up but so was my interval (197 hours) any insight on what could cause it to thicken up?

 

[Astro14]

Oxidation.

https://bobistheoilguy.com/motor-oil-104/

 

[fantastic]

What oil is this? Have you done a VOA on that oil?
EDIT: just seen it was Rotella 15w-40. Yeah that thickened up for certain. Was it Rotella T4 or T6?
Heat is one of the main contributor for oil thickening.

 

[notharry]

Engine Oil Oxidation​

• Thread starterOilUzer
• Start dateAug 21, 2024

Great post here. This will answer your question fully

 

[dnewton3]

Oxidation.

https://bobistheoilguy.com/motor-oil-104/

Also, soot; a byproduct of combustion.

 

[shortyb]

Oxidation.

Also, soot; a byproduct of combustion.

Both of which are pretty elevated in this sample IMHO.

 

[andyd]

How many engine hrs OCI ?