HT/HS of Used Oil?

[C4Dave]

Does anyone have any data on high temp/high shear of used oil? The reason I ask is that Ford has set a lower limit of 2.6 for the 5w20 spec. Some oils are right at 2.6 when new. What happens after 5000 miles? Does this number go down as viscosity goes down?

 

[buster]

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What happens after 5000 miles? Does this number go down as viscosity goes down?

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I believe it would, however, what we see with most 20wt oil is that they thicken and become 30wt oils.

Most modern engines can run on a 4cSt or greater viscosity oil.

 

[427Z06]

quote:

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Originally posted by buster:

quote:

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What happens after 5000 miles? Does this number go down as viscosity goes down?

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I believe it would, however, what we see with most 20wt oil is that they thicken and become 30wt oils.

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Is that generally the case, buster? I seem to vaguely recall that they stay the same or lower in viscosity, but I really haven't done a complete survey and analysis of a large number of dino 5w20 UOAs.

 

[JohnBrowning]

Their is no way to guess the HTHS of a used oil from what we see in UOA! It would have to be restested and I would imagine ASTM type testing is beyound most of here cost wise!

 

[Jay]

It's actually the SAE, not Ford, that sets the bottom HTHS limit for 20-weight at 2.6cP.

In my experience, M1 0w-20 thickens in service; MDC 5w-20 thins; Havoline 5w-20 neither thins nor thickens. All gave great wear results.

 

[MGBV8]

An oil like Redline should not be really effected.

With a dino or semi how are the viscosities at 0c 40c and 100c effected, and what influence would fuel dilution and soot have on these viscosities at these temperatures.