Motul 0W8 Has Same Viscosity as a 40 Grade Oil

[AEHaas]

...At around 165F. The viscosity should be around 15 and the HTHS should be around 3.5 (plus or minus). My 812 SF generally runs with an oil temperature of 165F while driving at 80 MPH. Ferrari owners manuals often specify a target oil pressure of 70 PSI at 6,000 RPM as being ideal. This oil would overshoot that recommendation for this application. Motor oil is viscosity dependant and should be chosen by the desired specification for the specific application.

ali

 

[4WD]

Go for it !

 

[kschachn]

...At around 165F. The viscosity should be around 15 and the HTHS should be around 3.5 (plus or minus). My 812 SF generally runs with an oil temperature of 165F while driving at 80 MPH. Ferrari owners manuals often specify a target oil pressure of 70 PSI at 6,000 RPM as being ideal. This oil would overshoot that recommendation for this application. Motor oil is viscosity dependant and should be chosen by the desired specification for the specific application.

Motor oil is viscosity dependent? What does that mean?

 

[FowVay]

Because most wear occurs at the upper portion of the cylinder wall, I wonder what the oil temperature is at the piston rings? I also wonder what the oil temperature is underneath the piston dome in the area of the wrist pins.

 

[demarpaint]

Motor oil is viscosity dependent? What does that mean?

Great question, temperature maybe? As long as the engine stays cold that oil might be like a 40 grade as the OP stated in the title? Eventually the engine will reach operating temp and the oil will be an 8 grade. Subscribed.........

 

[billt460]

Motor oil is viscosity dependant and should be chosen by the desired specification for the specific application.

If that's the case, then 0W-8 shouldn't be "chosen" for anything, except for use in Antarctica.

 

[aquariuscsm]

So a 10W-40 oil and Motul's 0W-8 are the same thickness up till 165F? Since engines run hotter than that (my gf's Olds 88 ran at around 225F when fully warmed), is that when the 0W-8's oil film would break, seizing the engine?

 

[BMWTurboDzl]

...At around 165F. The viscosity should be around 15 and the HTHS should be around 3.5 (plus or minus). My 812 SF generally runs with an oil temperature of 165F while driving at 80 MPH. Ferrari owners manuals often specify a target oil pressure of 70 PSI at 6,000 RPM as being ideal. This oil would overshoot that recommendation for this application. Motor oil is viscosity dependant and should be chosen by the desired specification for the specific application.

ali

165F at the oil temp sensor does not equate to 165F at the bearings.

 

[tasch72]

...At around 165F. The viscosity should be around 15 and the HTHS should be around 3.5 (plus or minus). My 812 SF generally runs with an oil temperature of 165F while driving at 80 MPH. Ferrari owners manuals often specify a target oil pressure of 70 PSI at 6,000 RPM as being ideal. This oil would overshoot that recommendation for this application. Motor oil is viscosity dependant and should be chosen by the desired specification for the specific application.

ali

So, how do we know that these two oils are the same viscosity at ~165*F?

 

[BMW Dom]

Here we go again

 

[wpod]

No oil is too thin on start up ,, what ever that means.

 

[OVERKILL]

So, how do we know that these two oils are the same viscosity at ~165*F?

He's using a visc calc.

So a 10W-40 oil and Motul's 0W-8 are the same thickness up till 165F? Since engines run hotter than that (my gf's Olds 88 ran at around 225F when fully warmed), is that when the 0W-8's oil film would break, seizing the engine?

I think he's saying that at 165F, he's calculated that Motul 0w-8 falls within the same range as an xW-40 at 100C (212F).

Since HTHS is specific to high temperature and high sheer, I'm not sure how one infers that it would be 3.5, given that it's measured at 150C. It wouldn't be HTHS if it was being measured at 165F. As @BMWTurboDzl pointed out, sump temp isn't the same as bearing temp and that's what HTHS is designed to replicate.

Since the good Dr. can clearly afford to replace the engine if it decides to play rod peek-a-boo, I say go for it, let's see what happens.

 

[slacktide_bitog]

Do you have any left over? Get a VOA done

And then a UOA when you change it again

 

[drtyler]

Is it a problem if the oil always operates at 165F and below?

 

[AEHaas]

Is it a problem if the oil always operates at 165F and below?

Good question. Eric Schneider's research on start-up wear revealed that the wear was least when the engine was at full operating temperature. So yes, it is probably better to have hotter oil but in my case I am not able to muster up all 800 HP long enough to heat it up.

Ali

 

[wpod]

Because most wear occurs at the upper portion of the cylinder wall, I wonder what the oil temperature is at the piston rings? I also wonder what the oil temperature is underneath the piston dome in the area of the wrist pins.

Why does most wear occur at TDC area? Because the piston slows to a stop and there is the combustion pressures blowing the oil down to the crankcase.

 

[ZeeOSix]

Since HTHS is specific to high temperature and high sheer, I'm not sure how one infers that it would be 3.5, given that it's measured at 150C. It wouldn't be HTHS if it was being measured at 165F.

Yeah, no way that any 0W-8 has the same HTHS as any xW-40 on Earth. Seems like BITOG tribology is going into the junk science realm.

 

[ZeeOSix]

Good question. Eric Schneider's research on start-up wear revealed that the wear was least when the engine was at full operating temperature. So yes, it is probably better to have hotter oil but in my case I am not able to muster up all 800 HP long enough to heat it up.

Ali

You don't have to make 800 HP to "heat it up". Go cruise around at 6000+ RPM in low gear while making less than 100 HP and see what happens to the oil temperature. Oil heats up mostly from shearing under high RPM conditions.

 

[bullwinkle]

Why does most wear occur at TDC area? Because the piston slows to a stop and there is the combustion pressures blowing the oil down to the crankcase.

I've always thought that as the piston changes direction, the side that's heaviest loaded on the way up abruptly switches to the other side for the down stroke.

 

[ZeeOSix]

Why does most wear occur at TDC area? Because the piston slows to a stop and there is the combustion pressures blowing the oil down to the crankcase.

The parts are losing mix/hydrodynamic lubrication. No speed, and the oil film essentially goes to zero.