HT/HS of Used Oil?

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507
Location
Tennessee
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?
 
Messages
34,225
Location
NJ
quote:
What happens after 5000 miles? Does this number go down as viscosity goes down?
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.
 
Messages
7,409
Location
Austin, TX
quote:
Originally posted by buster:
quote:
What happens after 5000 miles? Does this number go down as viscosity goes down?
I believe it would, however, what we see with most 20wt oil is that they thicken and become 30wt oils.

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.
 
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9,448
Location
USA
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

Messages
1,607
Location
Idaho Falls, ID
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.
 
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283
Location
uk
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.
 
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