Gibbs 5W-40 TD40 vs M1 0W-40 Lubrizol shear test

[Shannow]

Originally Posted By: CATERHAM
We know the viscosity after temporary shear. It's called HTHSV.


And it copped a pizzling in the test too...particularly if 3.5min is required by your engine.

 

[Shannow]

Originally Posted By: CATERHAM
Extreme shear stability is an overrated attribute of an oil, particularly if it comes at the expense of an oil's VI. It's more a selling feature of boutique oil formulators that like to over emphasis that their oils are not formulated with polymer VIs.


Hydrodynamics requires viscosity to work, and a thinner viscosity will always reduce the margin between asperite contact.

If you are already starting off with less headroom, then shear can/may/might make a big difference to the outcome

 

[CATERHAM]

Originally Posted By: Shannow

If you are already starting off with less headroom, then shear can/may/might make a big difference to the outcome

If you are running the spec' M1 0W-40 (HTHSV 3.85cP) in your Porsche or Mercedes, you're starting out with plenty of "headroom".
Going with the slightly lighter DT40 5W-40 (HTHSV 3.82cP) that's potentially more shear resistant is really second guessing the OEMs in terms of adequate viscosity retention in service.

Porsche states that oil shear has to exceed 18% before the oil is condemned and that applies to the lightest oils on the A40 list (HTHSVs as low as 3.6cP).

 

[A_Harman]

Originally Posted By: Shannow
And it copped a pizzling in the test too...particularly if 3.5min is required by your engine.


'...copped a pizzling..." ?!

Can you provide a translation into 'merican English for this Down Under term?

 

[A_Harman]

Originally Posted By: CATERHAM
Originally Posted By: Shannow

If you are already starting off with less headroom, then shear can/may/might make a big difference to the outcome

If you are running the spec' M1 0W-40 (HTHSV 3.85cP) in your Porsche or Mercedes, you're starting out with plenty of "headroom".
Going with the slightly lighter DT40 5W-40 (HTHSV 3.82cP) that's potentially more shear resistant is really second guessing the OEMs in terms of adequate viscosity retention in service.

Porsche states that oil shear has to exceed 18% before the oil is condemned and that applies to the lightest oils on the A40 list (HTHSVs as low as 3.6cP).


You're really down to splitting hairs when you take a .03 cP difference in HTHS and try to convince someone that it's going to have a material effect on engine life. If two oils are that close in HTHS, I would look at secondary considerations such as shear stability to make my decision about which oil to buy. I would pick the one that would be more likely to maintain its original viscosity.

 

[CATERHAM]

A_H you're right I was spitting hairs in the HTHSV difference of the two oils; it is indeed insignificant.

As mentioned I'm willing to concede that the lower VI DT 5W-40 is potentially more shear stable than the higher VI M1 0W-40, but that is a trade_off in M1's favour as long as it can maintain it's VI advantage in service (the test established that it can) plus the minimum operational viscosity the engine in question demands.