Is Shearing and Oxidation happening at the same time?

[Motor oil rookie]

They say both are happening. If oil shears or is thinining then why oxidation or thickening doesn't balance that out so that viscosity stays constant? Does one happen at a faster rate than the other? And eventually which one wins in most cases if you push the oil to its limit, does oil become too thin or does it become too thick? Please bear with my rookie questions.
Thank you

 

[userfriendly]

Viscosity loss from shearing is cancelled out by evaporation of the light ends.
-Noack

 

[JAG]

Viscosity loss is most rapid early on, then tapers off. That viscosity loss from shearing happens at a faster rate than oxidation. Eventually oxidation will slowly start raising the viscosity, but most people don’t run oils long enough for the viscosity to equal the virgin viscosity. If the oil is run extremely long so the remaining active antioxidants drop to a critical concentration, viscosity increase from oxidation rapidly rises. Outside of testing, the only people that run oils that long (likely >20k miles) are the utterly neglectful types who quickly ruin their engines.

Oils without viscosity index improvers experience negligible viscosity loss from shearing. Only the dispersants are prone to small amounts of permanent shearing.

 

[Motor oil rookie]

Viscosity loss is most rapid early on, then tapers off. That viscosity loss from shearing happens at a faster rate than oxidation. Eventually oxidation will slowly start raising the viscosity, but most people don’t run oils long enough for the viscosity to equal the virgin viscosity. If the oil is run extremely long so the remaining active antioxidants drop to a critical concentration, viscosity increase from oxidation rapidly rises. Outside of testing, the only people that run oils that long (likely >20k miles) are the utterly neglectful types who quickly ruin their engines.

Oils without viscosity index improvers experience negligible viscosity loss from shearing. Only the dispersants are prone to small amounts of permanent shearing.

Super helpful explanation. Thanks a ton. So the solution to this loss for me is to use a 0W-20 with no viscosity index improvers? Does such an oil exist?

 

[Motor oil rookie]

Viscosity loss is most rapid early on, then tapers off. That viscosity loss from shearing happens at a faster rate than oxidation. Eventually oxidation will slowly start raising the viscosity, but most people don’t run oils long enough for the viscosity to equal the virgin viscosity. If the oil is run extremely long so the remaining active antioxidants drop to a critical concentration, viscosity increase from oxidation rapidly rises. Outside of testing, the only people that run oils that long (likely >20k miles) are the utterly neglectful types who quickly ruin their engines.

Oils without viscosity index improvers experience negligible viscosity loss from shearing. Only the dispersants are prone to small amounts of permanent shearing.

Also, that rapid early viscosity loss is how rapid? First 1000 miles? And is it big enough that can turn a not so viscous 0W-30 into a very viscous 0W-20 like Red Line? Thank you

 

[JAG]

Super helpful explanation. Thanks a ton. So the solution to this loss for me is to use a 0W-20 with no viscosity index improvers? Does such an oil exist?

Other than boutique brands, I think most synthetic 0W-20 oils will have some VIIs. The closer the VI is to being around 140, generally the less the VII content. 5W-20 generally has less VIIs. Don’t put too much emphasis on it because the HTHS viscosity matters more than the kinematic viscosity at 100 C, and HTHS tends to drop from shearing at roughly 1/2 the amount of kinematic viscosity loss, on a percentage basis.

 

[JAG]

Also, that rapid early viscosity loss is how rapid? First 1000 miles? And is it big enough that can turn a not so viscous 0W-30 into a very viscous 0W-20 like Red Line? Thank you

1000 miles is enough to shear some oils that much, in my opinion. With Redline, I doubt it, but that’s without me looking up the virgin viscosity. I would expect less than .4 cST loss, assuming minor fuel dilution.

 

[Motor oil rookie]

1000 miles is enough to shear some oils that much, in my opinion. With Redline, I doubt it, but that’s without me looking up the virgin viscosity. I would expect less than .4 cST loss, assuming minor fuel dilution.

This is what I got from Blackstone ago

 

[Motor oil rookie]

1000 miles is enough to shear some oils that much, in my opinion. With Redline, I doubt it, but that’s without me looking up the virgin viscosity. I would expect less than .4 cST loss, assuming minor fuel dilution.

I checked HPL No VII, they come in 5W-20 only, no 0W-20.

 

[JAG]

Blackstone got the same viscosity as the PDS. Credit to them for that. The PDS says HTHS is 2.9 cP, which is higher than most xW-20 oils. See the typical properties section. https://www.redlineoil.com/0w20-motor-oil

I prefer their 5W-20 which has 3.1 cP HTHS viscosity, which is more than some xW-30 oils have.

 

[JAG]

I checked HPL No VII, they come in 5W-20 only, no 0W-20.

Probably too close to impossible and/or cost-prohibitive to make a 0W-20 without VIIs.

 

[Motor oil rookie]

Blackstone got the same viscosity as the PDS. Credit to them for that. The PDS says HTHS is 2.9 cP, which is higher than most xW-20 oils. See the typical properties section. https://www.redlineoil.com/0w20-motor-oil

I prefer their 5W-20 which has 3.1 cP HTHS viscosity, which is more than some xW-30 oils have.

Sir, is the difference between 0W-20 and 5W-20 at cold start such a big deal? I live in Seattle, temperature below 30 is literally for a week, not more than that. HPL No VII is 8.7 viscous and 3.2 HTHS. It should remain 8.7 till I am done with it. What an amazing oil.

 

[edyvw]

Sir, is the difference between 0W-20 and 5W-20 at cold start such a big deal? I live in Seattle, temperature below 30 is literally for a week, not more than that. HPL No VII is 8.7 viscous and 3.2 HTHS. It should remain 8.7 till I am done with it. What an amazing oil.

Only difference is at extreme negative temperatures, below -25 or -30.
In Seattle you can run straight 20 for all intended purposes.

 

[Motor oil rookie]

Only difference is at extreme negative temperatures, below -25 or -30.
In Seattle you can run straight 20 for all intended purposes.

Do oils have a value for cold flow speed? What is it called? Like how much faster is 0W than 5W at 40 degrees?
Thank you.

 

[edyvw]

Do oils have a value for cold flow speed? What is it called? Like how much faster is 0W than 5W at 40 degrees?
Thank you.

At 40 degrees, the difference is not measurable. I bet someone has somewhere some measurements, but this is how it is measured:
https://www.selectsynthetics.com/pa...s time, the SAE,heat and high load situations.

https://blog.amsoil.com/understanding-oil-viscosity/

 

[Motor oil rookie]

At 40 degrees, the difference is not measurable. I bet someone has somewhere some measurements, but this is how it is measured:
https://www.selectsynthetics.com/part-2--oil-viscosity-grades-.html#:~:text=By this time, the SAE,heat and high load situations.

https://blog.amsoil.com/understanding-oil-viscosity/

Thank you. I've decided to try HPL 5W-20 No VII. But I am not sure which one to pick for my 3.6L Wrangler. PCMO or Euro?

 

[edyvw]

Thank you. I've decided to try HPL 5W-20 No VII. But I am not sure which one to pick for my 3.6L Wrangler. PCMO or Euro?

Euro will have higher PAO content based on PDS. I would definitely go that.

 

[Motor oil rookie]

Euro will have higher PAO content based on PDS. I would definitely go that.

Great. Thanks!

 

[Motor oil rookie]

Blackstone got the same viscosity as the PDS. Credit to them for that. The PDS says HTHS is 2.9 cP, which is higher than most xW-20 oils. See the typical properties section. https://www.redlineoil.com/0w20-motor-oil

I prefer their 5W-20 which has 3.1 cP HTHS viscosity, which is more than some xW-30 oils have.

Sir you are right. This is even better. Amazing oil.

 

[OVERKILL]

Keep in mind, there are a variety of different VII polymers used and they vary in their shear resistance from "shear easily" to basically not at all.

Base oils also oxidize at different rates; have different levels of oxidation resistance and antioxidants are used to reduce the propensity to oxidize.

Formulators do indeed try and balance visc loss through shear with oxidation, and, as @userfriendly noted, light ends flashing off, which varies depending on the base oils used. However, a bigger factor in recent years, since the introduction of DI, has been fuel dilution.

This is what happens when you use shear stable VII's with PAO as the dominant base in an application that doesn't fuel dilute (sample 2 is VOA):