Turbo diesels, soot loading & turbo cooling.

[BMWTurboDzl]

I've been wondering if these two requirements compete with each other?
If 2 oils with similar HTHS but one is 30 and other is 40. Would the 30 provide marginal benefit to the turbos whereas a 40 would be better at soot loading?

What is the best balance or are the differences negligible?

 

[UG_Passat]

Diesel oils are designed with all that in mind.... some can start at a lower end of a weight to take into viscosity increases due to soot loading.

 

[Jim Allen]

By "soot loading" are you referring to the viscosity increase that comes or are you talking about the ability of an oil to disperse it and prevent agglomeration?

If the latter, there would really be no inherent difference between two similar oil formulations, 30 vs 40 grade. Some oil formulations may be better at it that others but the differences have nothing to do with viscosity and everything to do with the additive package.

If you mean viscosity increases, that happens pretty much at the end of the oil's useful life, so I don't think it's worth much thought. Significant thickening usually comes when the dispersants are pretty well used up and the oil is at it's soot percentage limit (generically 3% but it varies by engine).