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Obviously all fluids have viscosity so albeit an arbitrary way of labeling viscosity the system that we use for motor oil can only go so far without going negative or being adjusted accordingly. We are already down to 0w oil but that is obviously above zero cP so where does it go from here? Surley lower viscosities of oil are obtainable. Is SAE going to have to redefine its system or will we simply be talking of the newest -20w--5 and thinking people were insane for ever using 0w-20?
 
And apparently I am to dumb to realise there is already a topic about this.

Could someone merge this?
 
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It will never go into negative Ws, as Ws are for low temperature pumping, not really an operating viscosity...it's the same 0W starting point whether it's 0W16, or 0W50 that's being talked about.

What MIGHT happen is that they revert to the 30,000Cp pumping viscosity for the same temperature bands that was originally envisaged for J300 before the manufacturers pushed it to 60,000Cp.

IMO, the oil manufacturers were signalling their intent en masse to use GrIII rather than PAO for 0W.

e.g. here's the CAT TO-4 spec, which I'm lead to believe was based on early discussions on what was planned.

cat%20t04.jpg


30,000Cp at -45C is vastly different to 60,000Cp at -40C...using the doubling rule, the worst Cat TO-4 0W would be 15,000Cp at -40C.

So it will never get below 0W...although the definition of 0W may tighten to where it should have been.
 
Originally Posted By: jhellwig
And apparently I am to dumb to realise there is already a topic about this.

Could someone merge this?


Nah, leave it...it's about the W rating, the other one can go either way.
 
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