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#3176783 - 11/03/13 03:41 AM Shear Stability
Spooner65 Offline

Registered: 04/13/12
Posts: 44
Loc: California
I drive a 7.3L powerstroke, which utilizes a a high pressure oil pump that is notorious for shearing oil.

I want to learn what makes an oil shear stable. I have googled what I can, but cant find much in the way of instruction, just product descriptions and the such.
2002 Ford F250 7.3L

#3176807 - 11/03/13 05:55 AM Re: Shear Stability [Re: Spooner65]
Quattro Pete Offline

Registered: 10/30/02
Posts: 29537
Loc: Great Lakes
Originally Posted By: Spooner65
I want to learn what makes an oil shear stable.

Quality oil bases and low amounts of viscosity index improvers.
'02 530i (PPE 5W-40)
'15 Q5 3.0T (Edge 5W-40)

#3176859 - 11/03/13 07:30 AM Re: Shear Stability [Re: Spooner65]
gfh77665 Offline

Registered: 09/01/08
Posts: 2782
Loc: Southeast Texas
Mix in a qt. or two of single weight oil.

#3176874 - 11/03/13 07:41 AM Re: Shear Stability [Re: Quattro Pete]
gregk24 Offline

Registered: 04/13/13
Posts: 4048
Loc: FL, USA
Originally Posted By: Quattro Pete
Originally Posted By: Spooner65
I want to learn what makes an oil shear stable.

Quality oil bases and low amounts of viscosity index improvers.

This ^^^
2012 Honda Accord EX-L 34K
PPPP 0w20 / Fram Ultra

2005 Chevy Uplander 129K
GTX HM 5w30 / Fram Ultra

1991 Buick Park Avenue 118K
GTX HM 10w30 / Fram TG

#3176926 - 11/03/13 08:38 AM Re: Shear Stability [Re: Spooner65]
andyd Offline

Registered: 09/25/04
Posts: 4403
Loc: Marshfield , MA
No tribologist, but doesnt the same size molecules in synthetic oil help this too? I'm a cheap dino proponent, so I dont pay attention to this. laugh
2 1988 BMW 528e 20w50 dino, STP filter

1994 Ranger ,600$ Rat, 5w30 dino, STP filter

#3178225 - 11/04/13 01:30 PM Re: Shear Stability [Re: Spooner65]
Ken2 Offline

Registered: 12/02/02
Posts: 6358
Loc: Washington St.
Is there any good brand name 15W-40 diesel engine oil that will NOT do a good job in his 7.3? I think they all are formulated to work very well in that engine, very well in many other engines that use the engine oil as the hydraulic fluid in the injections system, and very well in many more engine designs.

Use the top brand name oil where you prefer the color of the label and sleep well. Your engine is well protected:
etc., etc.
Every gun that is made, every warship launched..a theft from those who hunger and are not fed, those who are cold and not clothed.
Gen. Eisenhower

#3178450 - 11/04/13 05:10 PM Re: Shear Stability [Re: Spooner65]
roadrunner1 Offline

Registered: 04/08/09
Posts: 944
Loc: oh
A 10w-30 is much more shear-stable in any HEUI system.
The shearing doesn't seem to hurt anything, but many of us have found that lighter oil definitely helps with cold starts.

5w-40 will also do the trick, just cost more. Also Chevron is offering a 5w-30 HDEO, I'm not sure if its even available yet but I have seen the advertisement.
'15 F350 6.7