I'm sorry if this is posted somewhere, I was having a hard time searching for this question, But I see over and over people stating that 20w's do a better job of not shearing out of viscosity than 30's do. I just want to know why? What is different about 5w30 that it shears down closer to a 5w20 by the end of the interval?
why is 5w20 more shear stable than 5w30?
- Thread starter Johnny248
- Start date
- Status
I was told a year or so ago that the base stocks the 20 grade oils were made from are better. IIRC it was from a Pennzoil rep.
Most 5w20's are made with very good base stocks.
Most Dino Xw30's are made with less expensive base stocks, but are vastly superior to what oils used to be.
Just wait until they start coming out with 0w10 oils for all these hybrid vehicles they have out there. Those will be interesting used oil analysis.
Most Dino Xw30's are made with less expensive base stocks, but are vastly superior to what oils used to be.
Just wait until they start coming out with 0w10 oils for all these hybrid vehicles they have out there. Those will be interesting used oil analysis.
A 5W-20 will never "shear out of viscosity" nor will any oil for that matter. Perhaps you mean "shear out of grade".
What's important is the amount of shear as a percentage of the virgin oil. 5W-20 grade oils tend to have lower a VI and less VII's than the so called broader range 5w30 grade and therefore are less prone to shear.
What's important is the amount of shear as a percentage of the virgin oil. 5W-20 grade oils tend to have lower a VI and less VII's than the so called broader range 5w30 grade and therefore are less prone to shear.
Doesn't directly answer your question but does provide good info'
All-Hydroprocessed Base Oils Eliminate Need for Expensive Correction Fluids:
Simplify Blending for GF-4
Tougher specifications have made it harder and harder for lubricant manufacturers to compete. Consequently, some blenders have been forced into elaborate three-way blending schemes, requiring two base oils and as much as 50% of expensive correction fluid. This cumbersome, inefficient solution requires additional base oil tanks and increases the chance of costly mistakes.
By using Chevron’s all-hydroprocessed Group II base oil you can produce GF-4 quality lubricants with a simple one step blending process. Because they are all-hydroprocessed, our base oils have:
higher purity
better oxidation stability
higher VI
lower CCS viscosity
lower volatility
Consequently, NO correction fluid is needed to meet GF-4 specs! Your additive supplier knows how to take advantage of Chevron's high-quality base stocks.
http://www.chevron.com/products/sitelets/baseoils/gf4.aspx
Chevron base oils
http://www.chevron.com/products/sitelets/baseoils/grp2_typical.aspx
All-Hydroprocessed Base Oils Eliminate Need for Expensive Correction Fluids:
Simplify Blending for GF-4
Tougher specifications have made it harder and harder for lubricant manufacturers to compete. Consequently, some blenders have been forced into elaborate three-way blending schemes, requiring two base oils and as much as 50% of expensive correction fluid. This cumbersome, inefficient solution requires additional base oil tanks and increases the chance of costly mistakes.
By using Chevron’s all-hydroprocessed Group II base oil you can produce GF-4 quality lubricants with a simple one step blending process. Because they are all-hydroprocessed, our base oils have:
higher purity
better oxidation stability
higher VI
lower CCS viscosity
lower volatility
Consequently, NO correction fluid is needed to meet GF-4 specs! Your additive supplier knows how to take advantage of Chevron's high-quality base stocks.
http://www.chevron.com/products/sitelets/baseoils/gf4.aspx
Chevron base oils
http://www.chevron.com/products/sitelets/baseoils/grp2_typical.aspx
My car calls for 5w30 and that's what I've been using, so I guess it would be ok for me to switch to 5w-20.
Even if it used the same base stock as 5W30 they could just leave out a lot of the VII and have a 5W20. With less VII to shear its going to be more stable. I wouldnt be suprised if some Synthetic 5W20 has no VII.
Originally Posted By: NightRiderQ45
My car calls for 5w30 and that's what I've been using, so I guess it would be ok for me to switch to 5w-20.
Not necessarily. Keep in mind this a general discussion only.
While a 5w30 may shear more than a 5W-20, at the end of a typical OCI the 5w30 will still be more viscous than the hypothetical 5W-20.
My car calls for 5w30 and that's what I've been using, so I guess it would be ok for me to switch to 5w-20.
Not necessarily. Keep in mind this a general discussion only.
While a 5w30 may shear more than a 5W-20, at the end of a typical OCI the 5w30 will still be more viscous than the hypothetical 5W-20.
Many 5w30 oils start on the low end of the 30 weight viscosity range (10-12.5cSt), while almost all 5W-20 oils start at the high end of the 20 weight viscosity range (6-9.5cSt). Since 5W-20 oils have farther to fall to get out of grade, few of them do. I've actually never seen a used oil analysis where a 20 weight oil has done this. Conversely, since 5w30 oils start off as being just barely in the 30 weight viscosity range, they don't have very far to fall before they're out of grade.
I wouldn't be surprised if 20 and 30 weight oils shear at exactly the same rates (percentage wise).
I wouldn't be surprised if 20 and 30 weight oils shear at exactly the same rates (percentage wise).
With regard to 5w30's shearing out of grade, I'm assuming this applies mainly to conventional oils? Or is this also a problem with 5w30 synthetics such as PP, Synpower, M1, etc? I'd assume that the synthetics should have less of, if any, problem with staying in grade. Please advise.
"Shearing out of grade" is a silly and misleading comment.
Most 20wt oils have a HTHS vis of 2.6 cP, the minimum for the grade, consiquently most 20wt oils will shear out of grade.
As I mentioned it is the percentage amount of shear vs the virgin oil that matters.
Most 20wt oils have a HTHS vis of 2.6 cP, the minimum for the grade, consiquently most 20wt oils will shear out of grade.
As I mentioned it is the percentage amount of shear vs the virgin oil that matters.
So is it the base stocks? or the Vii's? I don't understand why a manufacture would create a 5w20 oil using a higher quality base stock than their 5w30? So, would it be fair to say that something like Motorcraft 5w20 would stay in grade better than Amsoil 5w30 or 0w30? Or is apples to oranges comparing a premium syn 5w30 vs a standard 5w20?
We've been talking in generalities.
When it comes down to specific oils take a look at a few used oil analysis for that oil to determine it's propensity to shear.
Most Amsoil grades are very shear resistant.
When it comes down to specific oils take a look at a few used oil analysis for that oil to determine it's propensity to shear.
Most Amsoil grades are very shear resistant.
People have been beating around the bush here. Here is the basic principle, as far as I know it. Look at these two numbers "5w20" then look at these two numbers "5w50." Which ones are farther apart? According to my understanding, oil companies would start both these oil base stocks with about the same viscosity stock. They would then add a different amount of viscosity index improver to each.
Basically the viscosity index improvers (VII) are molecules that stretch out as they get hotter and therefore create a thicker oil. Now guess which one has more VII added?
The correct answer is 5w50.
Now that's all fine and dandy because you can make an oil that pumps really well when at -25 degrees at cold start and can run at +200 degrees at 8000rpm on a 24hour Le Mans Race.
But if you are a chemist (I've only taken a few college level courses in it)you know that longer molecule chains are more susceptible to mechanical stress i.e. "shearing". In essence that means that when the oil is hot and the VII molecules are expanded, they are very vulnerable to shearing, so a racer pushing 9000rpm on his tuned Dodge Viper ACR, probably wouldn't do well with a single fill of 5w50 for 24hours of endurance racing. He would need a 15w50 or a 20w50, or even a HDEO 15w40, according to the principle.
Those are my 2cents
Basically the viscosity index improvers (VII) are molecules that stretch out as they get hotter and therefore create a thicker oil. Now guess which one has more VII added?
The correct answer is 5w50.
Now that's all fine and dandy because you can make an oil that pumps really well when at -25 degrees at cold start and can run at +200 degrees at 8000rpm on a 24hour Le Mans Race.
But if you are a chemist (I've only taken a few college level courses in it)you know that longer molecule chains are more susceptible to mechanical stress i.e. "shearing". In essence that means that when the oil is hot and the VII molecules are expanded, they are very vulnerable to shearing, so a racer pushing 9000rpm on his tuned Dodge Viper ACR, probably wouldn't do well with a single fill of 5w50 for 24hours of endurance racing. He would need a 15w50 or a 20w50, or even a HDEO 15w40, according to the principle.
Those are my 2cents
- Joined
- Sep 28, 2002
- Messages
- 39,793
Originally Posted By: Gene K
Even if it used the same base stock as 5W30 they could just leave out a lot of the VII and have a 5W20. With less VII to shear its going to be more stable. I wouldnt be suprised if some Synthetic 5W20 has no VII.
Yeah, take a more shear prone 5w30 ..and forget to put in the VII. Voila~! ..shear stable 5w-20.
Even if it used the same base stock as 5W30 they could just leave out a lot of the VII and have a 5W20. With less VII to shear its going to be more stable. I wouldnt be suprised if some Synthetic 5W20 has no VII.
Yeah, take a more shear prone 5w30 ..and forget to put in the VII. Voila~! ..shear stable 5w-20.
- Status
Similar threads
- Locked
- Locked
- Locked