Why the large difference between oils viscosities?

[The_Eric]

I'm comparing two oils right now. Rotella T6 5w-40 and Mobil 1 Turbo Diesel 5w-40. As with other brands and grades, there is a sizable difference between the two viscosities at 40c.. The Mobil is a shade over 100 and the Rotella is in the upper 80's... Why, if they're both 5w oils is there so much difference? As far as I can discern, the T6 is more like a thick 5w and the Mobil is more like a thick 10w... The 100c viscosities are closer together in the 14 range...

Moving on to drawing conclusions, would that mean that the Mobil would likely be more shear stable? It's HT/HS is 3.9 while so far I haven't been able to find the T6's...

 

[Audi Junkie]

Different starting viscs accounts for the amount of shear experienced during service. Take Havoline DS 30, it's on the verge of being a 20, but has a shear-proof add pack, so it makes wear spec, no problemo.

Other oils maybe be thicker, and I snicker when posters come on demanding "the thickest X oil", afaik, that just means they want the oil that is likely to shear the most.

 

[daman]

It's just how the Manufacture chooses to blend there oil for shear purposes i would think, the M1 is HT/HS 3.9 should be a very stable oil.

Mobil 1 Turbo Diesel Truck is a great oil,they both are.

 

[bluesubie]

They both may shear, depending on the application IMO.

There are some Subaru turbo used oil analysis on both oils where the viscosity sheared to a 30 grade. A few of the RTS used oil analysis are in the used oil analysis forum here (on WRX's/STI's/Legacy GT's) and there are a few Mobil 1 Turbo Diesel Truck used oil analysis over at subaruforester.org in a turbo Forester in FL that tows.

They're both good oils though. You can make yourself cuckoo by trying to decide on an oil based on product data sheets or used oil analysis.

-Dennis

 

[The_Eric]

So this brings me to ask- why isn't oil viscosity a standard? Why are some 5w, 10w or whatever thicker or thinner at 40c and/or 100c?? I'd think that should be an industry standard...

 

[znode]

Originally Posted By: The_Eric
So this brings me to ask- why isn't oil viscosity a standard? Why are some 5w, 10w or whatever thicker or thinner at 40c and/or 100c?? I'd think that should be an industry standard...


It is.

It just isn't standardized on kinematic viscosity.

 

[The_Eric]

Thanks for the link and the info!

 

[Quattro Pete]

Originally Posted By: The_Eric
Moving on to drawing conclusions, would that mean that the Mobile would likely be more shear stable? It's HT/HS is 3.9 while so far I haven't been able to find the T6's...

Old Rotella T 5w-40 had an HT/HS of 4.2. Not sure how this has changed for the T6, if at all.

Oh, and there is no 'e' in Mobil.

 

[The_Eric]

Originally Posted By: Quattro Pete
Originally Posted By: The_Eric
Moving on to drawing conclusions, would that mean that the Mobile would likely be more shear stable? It's HT/HS is 3.9 while so far I haven't been able to find the T6's...

Old Rotella T 5w-40 had an HT/HS of 4.2. Not sure how this has changed for the T6, if at all.

Oh, and there is no 'e' in Mobil.

Thanks ya spelling Nazi!!! Kidding...

In all seriousness, thanks for the heads up on the HT/HS and the unnecessary "e". Where did you find that info? And I'm not talking about the spelling either.

 

[Quattro Pete]

Quote:
Where did you find that info?

Someone on a another forum contacted SOPUS and that's they answer they received via email from a SOPUS customer rep. It was a while back though.