VII & Shear Avoidance

[ProfPS]

Over the past couple years there have been many posts regarding 5w30 VII's and shearing. Since many have also posted that 5W-20 and 10w30 have less VII's and shear less than 5w30, what about a 5W-20/10W-30 mix?? For 5w30 apps mix 5W-20 with 20-30% 10w30.

Would this produce a preferred mix that have less VII's and is more shear stable?

 

[mcrn]

Right now I have 5 quarts of Pennzoil Conventional 10w30 and 1 quart of 5W20. So I am curious about this as well.

 

[glenncof]

Your question has several dimensions (I won't cover all of them). Here is what I think.

The best way to get shear stability (in multi-grade)is to use oil containing the best VI base oil and use less VII. Oils have improved quite a bit in the last several years so it's less of an issue especially in the grades your talking about. (Think about a 0W40, a 5W50, or a 10W60!)

Then again it depends how long OCI and we are asking more of our oils in this regard.

So I hunt for the best base. I don't mean to jump on the bandwagon but PP (Grp III Shells VHVI base?) and their YB (likely GrpII+) are current top on my list. But I use others also like Quaker State Synthetic, MC 5W20 and SynPower based on price, also I can't push OCI out.

When I blend I expect to get less than absolute best performance from the add pack. So if you're looking for longer OCI I would generally avoid. Blending same brand probably has least risk (but not guaranteed).

So your question is a complex one with unknowns and I believe on this basis alone the risk out ways the reward.

 

[glenncof]

Alternatives would be to use GC 0W30 (see section on Euro oils) or use a _W30 that is ACEA A3 rated (eg. Mobil 1 10W30 HM or Maxlife Synthetic) but this may be costly. A3 = better HTHS.

 

[Drivebelt]

Quote:
what about a 5W-20/10W-30 mix?? For 5w30 apps mix 5W-20 with 20-30% 10w30.


Lets look at that mix …

……………………cSt
70% … 5W-20 … 8.6
30% … 10w30 … 10.5

resulting blend … 9.17

So, the blend will end up below a 30 weight (9.3 - 12.5 cSt range).

Your typical 5w30 is around 10.6 cSt. So that 5w30 would have to shear down quite a bit to get to 9.17 cSt.

I was looking at some used oil analysis by Blackstone a while ago, and I must say their 100C viscosity numbers look low. I don't know how Blackstone is measuring the 100C viscosity numbers. Perhaps they measure the viscosity at 40C and use a formula to estimate, or calculate the 100C viscosity, but they show virtually all 5w30's shearing down to the 20 weight range in virtually all applications -- which I am skeptical of.

There was a recent VOA of Rotella T synthetic 5W-40 where the viscosity came back as 13.36. According to the data sheet, Rotella 5W-40 is 15.5 cSt. I don't believe there is any way possible that the variance in blending of Rotella T Synthetic by Shell would be out by that much variance on any batch. I could believe maybe a 0.5 cSt variance, but not over 2.0 cSt.

 

[Tempest]

I think the lubrication engineers that originally designed the oil in the first place know more about this than anyone on this board.

 

[ProfPS]

Thanks for everyone's responses. I see VII and shearing comments popping up every now and then, and thought there might be a way around it since I am also seeing more posts about home blending. It is just food [crude] for thought.