HTHS and oil temperature.

[bajatool]

Hello, I am trying to understand how hths works with different oil weights, and if it varies with temperature. Please bear with me, as I am a newbie

. My car specs out 20 weight, which in general will have a lower hths than a 30 weight, which in turn will have a lower hths than a 40 weight etc. Is the hths rated at a 100c though? At a lower temperature would hths be higher for any given weight? Would the hths of the 20 weight oil be higher in my engine operating condition if my temperature never gets up to 100c? Conversly would a heavier oil in a hotter engine possibly have a lower hths than the 20 weight oil operated in a relatively cooler engine? Hope I'm not way off base with this..

Thanks

 

[Bryanccfshr]

The HTHS measurement is @150°c.

 

[bajatool]

So far only 50c off base...

 

[427Z06]

No, 150°C.

To answer your other questions, let's define HTHS first. HTHS is defined as measuring the absolute viscosity of the oil at a specific temperature under specific conditions using a specific method, namely when being highly sheared.

So at other temperatures, you'd be measuring the absolute viscosity under specific conditions using a specific method. It's possible that the lower viscosity oil at a lower temperature would have a higher absoulte viscosity than a higher viscosity oil at greater temperatures when measured as outlined above.