Question about the cSt of oil

[illby1]

I have been reading on this forum as much as I can and it seems like 10cST @100c is what we are aiming for,right?

The reason I am asking is because the oil's I am looking at using have lower numbers than that....
Mobil 1 0W-20 AFE is 8.5cSt @ 100c
Mobil 1 5W-20 is 9.0cSt @ 100c
Valvoline Synpower 0W-20 is 8.8cSt @ 100c
Valvoline Synpower 5W-20 is 8.65 @ 100c

How close to 10cSt am I aiming for?? The higher the better?
Is 8.5/9.0 "close enough"

 

[ARCOgraphite]

Where did you read "we are aiming for 10cst"? That would be a thin 30 weight - not a 20 weight. A little knowledge is a dangerous thing ... . Me, I aim for 10.7 in the toyota.

 

[barlowc]

On average, a 5W-20 synthetic is around 8.75 and a 5W-30 synthetic is around 10.5.

 

[d00df00d]

Originally Posted By: illby1
I have been reading on this forum as much as I can and it seems like 10cST @100c is what we are aiming for,right?

Where did you read that?

cSt is a measure of what is called kinematic viscosity. The best number (or range of numbers) depends on the car. Some cars work best with oils that are as high as 25 cSt @ 100C; others need oils as low as 8 cSt. Many don't care much about kinematic viscosity at all, but need high temperature/high shear (HTHS) viscosity to be above or below a certain level.

When you look at the viscosity rating on oils (e.g. 5w-20, 10w-30, etc.), the big number after the hyphen represents a range of cSt numbers: 20 means 5.6-9.29 cSt @ 100c, 30 means 9.3-12.49 cSt @ 100C, and so on. The oil recommendation in your owner's manual will give you some hints on what kinds of viscosity your engine prefers. Again, it's different for every car, so there is no single magical number to shoot for.

 

[CATERHAM]

I have been reading on this forum as much as I can and it seems like 10cST @100c is what we are aiming for,right?

The reason I am asking is because the oil's I am looking at using have lower numbers than that....
Mobil 1 0W-20 AFE is 8.5cSt @ 100c
Mobil 1 5W-20 is 9.0cSt @ 100c
Valvoline Synpower 0W-20 is 8.8cSt @ 100c
Valvoline Synpower 5W-20 is 8.65 @ 100c

The KV100 spec' you're referring is a red herring.
You should be looking at the HTHS vis spec.
All light 20wt oils with the same HTHS vis of 2.6cP have the same operational viscosity regardless of their KV100 spec's
Same for heavier 2.7cP mid-grade 20wt oils and heavy 2.8cP 20wt's.



Check out the attached, it may clarify how viscosity is measured for you:

https://bobistheoilguy.com/forums/posts/2018835/

 

[illby1]

Originally Posted By: ARCOgraphite
Where did you read "we are aiming for 10cst"? That would be a thin 30 weight - not a 20 weight. A little knowledge is a dangerous thing ... . Me, I aim for 10.7 in the toyota.


Originally Posted By: d00df00d
I have been reading on this forum as much as I can and it seems like 10cST @100c is what we are aiming for,right?
Where did you read that?


http://www.bobistheoilguy.com/cms/index.php?option=com_content&view=article&id=80

The paragraph that I was reading is as follows:
The thickness of moving oil is measured in centiStokes or cS. Most engines want the oil viscosity to be around 10 cS at normal operating temperature. The really thick multi-grade oils have a viscosity of 20 cS at operating temperature. One is not twice as thick as the other, it is only 10 cS thicker.

So, I was looking for an Synthetic oil that was around 10cS at operating temperature.
I guess my question was if the oils that I was looking at were in the 8.5/9.0 range are they going to be ok?

 

[Quattro Pete]

Originally Posted By: illby1

I guess my question was if the oils that I was looking at were in the 8.5/9.0 range are they going to be ok?


It depends on the application. Care to give us some more details: what car, what engine, what are the driving patterns, etc.?

There is no single right answer, just as there is no such thing as best oil.

 

[Steve S]

Just because it is on the internet !!!

 

[[RT] ProjUltraZ]

jeez tough crowd. and a little knowledge is not always dangerous, depends who receives it. but i think the answer to his question is: stick to the manufacturer's recommendation for oil weight on a stock vehicle, and yes 20 weights are in that range

 

[d00df00d]

Quote:
Most engines want the oil viscosity to be around 10 cS at normal operating temperature.

This line is referring to the fact that, at the time the article was written, most engines call for an xw-30 oil -- i.e. an oil with a viscosity grade of 0w-30, 5w-30, or 10w-30. An xw-30 will be somewhere around 10 cSt @ 100C. It's not meant as advice; it's just stating that that's the most commonly used range, and using that number as an example to make a point.

Also, more and more cars these days are calling for xw-20 oils (like the oils you're looking at). So, even if it were advice, it'd be obsolete.

Quote:
I guess my question was if the oils that I was looking at were in the 8.5/9.0 range are they going to be ok?

If your owner's manual specifies an xw-20, then yes.

Keep in mind that viscosity is FAR from the only thing when choosing oils. Your manual may also specify that your oil needs to have certain approvals (e.g. API SM, ILSAC GF-4, etc.), or make specific brand recommendations. Make sure you know what those are before picking your oil.

 

[XS650]

Originally Posted By: [RT
ProjUltraZ]jeez tough crowd. and a little knowledge is not always dangerous, depends who receives it. but i think the answer to his question is: stick to the manufacturer's recommendation for oil weight on a stock vehicle, and yes 20 weights are in that range


That is good advice unless you are doing something extreme that is well out of the limits of normal vehicle operation.

 

[mechtech2]

illby1 -
If your car call for a 5-20, then great! There are some advantages for cold weather, power, and gas economy.
If the vehicle call for a 5-30, then I'd use it instead, esp. in summertime.

 

[Jakegday]

now i have a question regarding this...

from looking at the CSTs for mobil 1, it appears 5w30 is actually thicker then the 10w30. with that in mind, should a person run the 10w30 in the winter, and 5w30 in the summer?

 

[Quattro Pete]

Originally Posted By: Jakegday
now i have a question regarding this...

from looking at the CSTs for mobil 1, it appears 5w30 is actually thicker then the 10w30. with that in mind, should a person run the 10w30 in the winter, and 5w30 in the summer?

M1 5w-30 is slightly thicker at operating temp, but on a cold winter morning, it'll be less thick than M1 10w-30. You don't want 10w-XX in your engine when it's really cold out.

This was recently discussed, by the way:
https://bobistheoilguy.com/forums/threads/another-mobil-1-question.139520/

 

[CATERHAM]

Originally Posted By: Jakegday
now i have a question regarding this...

from looking at the CSTs for mobil 1, it appears 5w30 is actually thicker then the 10w30. with that in mind, should a person run the 10w30 in the winter, and 5w30 in the summer?


HTHS viscosity is the accurate measure of how "thick" an oil is, not the kinematic viscosity spec' your looking at.
M1's 10W-30 not surprisingly has a higher HTHS vis than for their 5W-30 grade and therefore is the more viscous at normal operating temp's and higher.
This question has been posted before:

http://www.bobistheoilguy.com/forums/ubb...672#Post2021672

 

[illby1]

Originally Posted By: Quattro Pete
Originally Posted By: illby1

I guess my question was if the oils that I was looking at were in the 8.5/9.0 range are they going to be ok?


It depends on the application. Care to give us some more details: what car, what engine, what are the driving patterns, etc.?

There is no single right answer, just as there is no such thing as best oil.



1. 2011 Hyundai Sonata
2. The manual calls for API Service SM ILSAC GF-4 or above.
5W-20 with 7,500 oci and 3,750 for extreme driving conditions...
3. Northern Wisconsin
4. 4 mile commute to work,longer trips on the weekends
5. Mostly short trips to and from work and errands...Longer road trips on the weekends
6. No issues with my car at all...

 

[CATERHAM]

Sorry Quattro Pete, you beat me to it!

 

[ARCOgraphite]

Originally Posted By: CATERHAM


... HTHS viscosity is the accurate measure of how "thick" an oil is, not the kinematic viscosity spec' your looking at.
M1's 10W-30 not surprisingly has a higher HTHS vis than for their 5W-30 grade and therefore is the more viscous at normal operating temp's and higher.
...

I tried to explain that to my oil pump during a -10F cold start and it just went, "grunt ... Grunt"

 

[d00df00d]

Originally Posted By: ARCOgraphite
Originally Posted By: CATERHAM


... HTHS viscosity is the accurate measure of how "thick" an oil is, not the kinematic viscosity spec' your looking at.
M1's 10W-30 not surprisingly has a higher HTHS vis than for their 5W-30 grade and therefore is the more viscous at normal operating temp's and higher.
...

I tried to explain that to my oil pump during a -10F cold start and it just went, "grunt ... Grunt"

Sorry, CATERHAM. He's got you there. HTHS is an important spec but it's no more "accurate" than kinematic viscosity.

 

[d00df00d]

Originally Posted By: illby1
1. 2011 Hyundai Sonata
2. The manual calls for API Service SM ILSAC GF-4 or above.
5W-20 with 7,500 oci and 3,750 for extreme driving conditions...
3. Northern Wisconsin
4. 4 mile commute to work,longer trips on the weekends
5. Mostly short trips to and from work and errands...Longer road trips on the weekends
6. No issues with my car at all...


Well then you definitely don't want to shoot for 10 cSt.

Any 5w-20 or 0w-20 that meets API SM and ILSAC GF-4 should work. The differences in viscosity among them will be minor; your engine probably won't notice.