Long term effects of shearing?

[Quick_lude]

What would they be and how long before they affect the engine, if at all?
Scenario, the new 6.0 PSD in the F series superduty truck is very hard on oil viscosity. If you take a look at the 6.0 oil analysis study located here: Oil Study you will see that this engine, shears most if not all 40 weight oils to a 30 weight at 5,000 mile intervals. Some people theorize that once this viscosity is achieved, it levels off at 30. My own analysis showed the Esso XD-3 0w40 shearing from 15 Cst to 9.8 in 8000km.

So my question is, what are the long term effects of such shearing? Sludge build up? Seal problems? What kind of preventitive maintenance action can be taken (Auto-RX/LC?) to make sure this engine runs well for 200K km and beyond?

 

[TallPaul]

If a 10w40 sheers back to a 10w30 will it be significantly inferior to the off-the-shelf 10w30? If I get an oil that consistently sheers that much (only way I can tell is if oil pressure drops), then I will find a different brand or grade to run.

 

[XS650]

quote:

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Originally posted by TallPaul:
If a 10w40 sheers back to a 10w30 will it be significantly inferior to the off-the-shelf 10w30? If I get an oil that consistently sheers that much (only way I can tell is if oil pressure drops), then I will find a different brand or grade to run.

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Somone in another thread ran a bunch of comparative viscosity tests by timing how long it took 1 ounce of oil to drain through a 1/10 inch hole. If you did the same with some new 30 and 40, then you would have a baseline to check sheardown in your 10W-40.

 

[TallPaul]

quote:

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Originally posted by XS650:
Somone in another thread ran a bunch of comparative viscosity tests by timing how long it took 1 ounce of oil to drain through a 1/10 inch hole. If you did the same with some new 30 and 40, then you would have a baseline to check sheardown in your 10W-40.

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Great idea, but my wife is ready to kill me already for the amount of time I spend playing around in the garage.

Given that 30 wt gives me about 35 psi and 40 wt gives me about 44 psi, I fully expect a permanent viscosity collapse to show up in the oil press gauge.

 

[williar]

The link to the "oil study" didn't work for me, but as far as shearing from a 40w to a 30w goes I doubt that, in itself, it has any harmful effects. You're just running with a xW30 oil. Of course by the time the oil shears to a 30w it's time to replace it anyway because it's TBN is low and it's contaminated.

 

[Quick_lude]

The link works for me, it should show a file structure, click on the 6.0.pdf file or just click HERE

My oil analysis of the XD-3 0w40 at 8,000km HERE showed a tbn of 8.3 from 12.5. Plenty of tbn left.