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#4771001 - 05/29/18 09:34 AM Is there a slight bump up in MPG as oil shears?
Speak2Mountain Offline


Registered: 04/07/17
Posts: 346
Loc: Mississippi
or are there other factors in play?

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#4771007 - 05/29/18 09:40 AM Re: Is there a slight bump up in MPG as oil shears? [Re: Speak2Mountain]
kschachn Offline


Registered: 12/26/05
Posts: 9381
Loc: Upper Midwest
When does oil shear?
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#4771021 - 05/29/18 09:58 AM Re: Is there a slight bump up in MPG as oil shears? [Re: Speak2Mountain]
dlundblad Offline


Registered: 09/30/13
Posts: 10011
Loc: Indiana
Theoretically yes.

Is it measurable though?
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#4771022 - 05/29/18 09:59 AM Re: Is there a slight bump up in MPG as oil shears? [Re: kschachn]
dlundblad Offline


Registered: 09/30/13
Posts: 10011
Loc: Indiana
Originally Posted By: kschachn
When does oil shear?


Check out UOA's from EB engines. They'll shear oil from a 5w30 to a 5w20. It's the whole reason Ford back spec'd most of them to 5w30.
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97 Chevy Blazer 4.3 145k Rotella T5 10w30 Fram TG3980


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#4771024 - 05/29/18 10:00 AM Re: Is there a slight bump up in MPG as oil shears? [Re: kschachn]
CT8 Offline


Registered: 10/09/14
Posts: 10930
Loc: Idaho
Originally Posted By: kschachn
When does oil shear?
Oil [mulit visc oils] shears between the moving parts as the engine is running
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#4771029 - 05/29/18 10:02 AM Re: Is there a slight bump up in MPG as oil shears? [Re: Speak2Mountain]
Reddy45 Offline


Registered: 08/15/08
Posts: 2963
Loc: USA
This came up during a recent discussion.

Oil can shear slightly with use, but as the more volatile components of oil evaporate with use, it has a thickening effect.

So the net effect is more or less 0.

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#4771035 - 05/29/18 10:09 AM Re: Is there a slight bump up in MPG as oil shears? [Re: Reddy45]
dlundblad Offline


Registered: 09/30/13
Posts: 10011
Loc: Indiana
Originally Posted By: Reddy45
This came up during a recent discussion.

Oil can shear slightly with use, but as the more volatile components of oil evaporate with use, it has a thickening effect.

So the net effect is more or less 0.


I didnt think of thickening.
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#4771159 - 05/29/18 12:27 PM Re: Is there a slight bump up in MPG as oil shears? [Re: Speak2Mountain]
benjy Offline


Registered: 08/23/10
Posts: 865
Loc: pa
another reason to use better oils + real synthetic groups IV + V are the BEST. less shear + less viscosity improvers that get used up + thicken oils!!

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#4771170 - 05/29/18 12:44 PM Re: Is there a slight bump up in MPG as oil shears? [Re: benjy]
kschachn Offline


Registered: 12/26/05
Posts: 9381
Loc: Upper Midwest
An often made statement, but as far as I've seen without merit. SonofJoe has repeatedly stated that modern viscosity improvers are very stable and are highly resistant to shear degradation. Also, how would you even know if the typical Blackstone analysis that shows viscosity loss is due to shear or fuel dilution?

Originally Posted By: benjy
another reason to use better oils + real synthetic groups IV + V are the BEST. less shear + less viscosity improvers that get used up + thicken oils!!
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1994 BMW 530i, 227K
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#4771370 - 05/29/18 04:27 PM Re: Is there a slight bump up in MPG as oil shears? [Re: Reddy45]
rrounds Offline


Registered: 07/05/07
Posts: 950
Loc: SACRAMENTO, CA
Originally Posted By: Reddy45
This came up during a recent discussion.

Oil can shear slightly with use, but as the more volatile components of oil evaporate with use, it has a thickening effect.

So the net effect is more or less 0.

There are 100's of UOA's on here alone that show oil sheared out of grade(little or no fuel in oil) and on the motorcycle section you will find most bikes with a shared transmission get oil thats sheared out of grade in 4000 miles or less. Sometimes a lot less miles, my old R6 would only get 2500 miles on its oil before it would shear and make shifting real notchy.

ROD
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#4771439 - 05/29/18 05:49 PM Re: Is there a slight bump up in MPG as oil shears? [Re: Speak2Mountain]
ZeeOSix Offline


Registered: 07/22/10
Posts: 17767
Loc: PNW
I keep track of my oil level carefully, and always see the consumption starts low, then starts to increase after about 300~400 miles are put on the oil. All I can think is that oil is shearing down some which increases the oil consumption enough to see it.

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#4781165 - 06/08/18 10:52 AM As oil shears w/miles; shouldn't MPG bump up
Speak2Mountain Offline


Registered: 04/07/17
Posts: 346
Loc: Mississippi
slightly bc of it being thinner

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#4781170 - 06/08/18 10:58 AM Re: As oil shears w/miles; shouldn't MPG bump up [Re: Speak2Mountain]
kschachn Offline


Registered: 12/26/05
Posts: 9381
Loc: Upper Midwest
Didn't get the answer you wanted the last time or??

https://www.bobistheoilguy.com/forums/ub...n_M#Post4771001
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1994 BMW 530i, 227K
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1999 Toyota Sienna, 394K
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#4781172 - 06/08/18 10:59 AM Re: As oil shears w/miles; shouldn't MPG bump up [Re: Speak2Mountain]
PimTac Offline


Registered: 03/04/17
Posts: 4234
Loc: Soviet State of Washington
I thought this had been asked before, didnít know it was the same poster.
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#4781178 - 06/08/18 11:05 AM Re: As oil shears w/miles; shouldn't MPG bump up [Re: PimTac]
kschachn Offline


Registered: 12/26/05
Posts: 9381
Loc: Upper Midwest
And only a little over a week ago.
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1994 BMW 530i, 227K
1996 Honda Accord, 262K
1999 Toyota Sienna, 394K
2000 Toyota ECHO, 267K

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