Viscosity change vs oil temps

Pennzoil motor oil
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MilesO

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We are all familiar with the many combinations of multi-viscosity oils used now.

I am interested in the oil temperature at which a multi-grade oil changes from 5wt to 10wt to 20wt to 30wt to 40wt to 50wt .

Is there an industry standard relative to this relationship or is there no standard to be met ?

Where can I find this informnation most directly ?

Your replies are appreciated .
 
Thanks for your quick reply. I have seen similiar charts but they don't provide the answer.

As the engine operating temp increases from ambient temp the engine oil temp moves from ambient temp through its operating temp range.

A multi-grade oil, ie; 5-50wt, at certain design temps, meets the criteria of a 10wt, 30wt, 50wt oil as its operating temp rises.

I want to know at what temperature does a multi-weight oil meet the criteria of a 30wt, 40wt, 50wt oil.

I hope this helps .
 
Originally Posted By: MilesO
A multi-grade oil, ie; 5-50wt, at certain design temps, meets the criteria of a 10wt, 30wt, 50wt oil as its operating temp rises.

I'm not sure I follow you. A 5w-50 oil is going to always be a 5w-50 oil, regardless of what temperature it's operating at.
 
use a viscosity calculator to find the temps where it falls into the various weights. that would be interesting to see someone graph that out
 
Quote:
I want to know at what temperature does a multi-weight oil meet the criteria of a 30wt, 40wt, 50wt oil.



A 10w-50 appears like a 50 weight @ 100C/212F
A 0w-40 appears like a 40 weight @ 100C/212F (in case of M1 - for a while anyway)
A 20w-20 appears like a 20 weight @ 100c/212F
A 0w or 5w- 20 appears like a 20 weight @ 100C/212F


That doesn't answer your question, but your question cannot give you want you're seeking here by how it's worded as I sense your confusion.

The HOT visc (212F/100C) is the 20,30,40,50,60,70 part of the multivisc designation.

Hence a (x)W-20/30/40/50/60/70 will have a viscosity that falls into those ranges @ 100C/212F ..but have cold performance characteristics of the lower (W) number at colder temps (sub zero).
 
Gary,
I am after the temp at which the performance characteristics of the multi-grade oil meets the 'weight specification' to be called a 30wt, 40wt, 50wt as its temp rises during engine operation. I am not concerned with the cold temp character of the oil.

Thanks for the link, I may be able to use one of the links in it if I am able to learn the criteria for the varius wt oils.
 
Originally Posted By: MilesO

A multi-grade oil, ie; 5-50wt, at certain design temps, meets the criteria of a 10wt, 30wt, 50wt oil as its operating temp rises.



That is not how oil works, it is a common misconception so you are not alone out there in your reasoning. A 5w50 oil will never be a 5w oil unless you dilute the heck out it with gas or something. Oil starts out thicker than the second number weight (in this example a 50w) and thins down to the 50w spec but never thins to a say 30w (unless at extreme temps I guess).
 
Last edited:
Originally Posted By: MilesO
I am after the temp at which the performance characteristics of the multi-grade oil meets the 'weight specification' to be called a 30wt, 40wt, 50wt as its temp rises during engine operation. I am not concerned with the cold temp character of the oil.

The 'weight specification' is measured at 100C (212F), as Gary pointed out. They are all measured at this temperature, and depending on which viscosity range they fall into, they are then classified as Xw-30, Xw-40, Xw-50, etc.
 
Hoosier,
That may be the only way. As I replied to Gary, I just need the criteria for 30-50wt oils, the link he provided may contain another link to allow me to figure it.

The only concern I have with that is.. does the multi-grade oil, say 5w-50wt, meet the weight criteria at the same temp as a single wt oil would ? My answer may prove to be brand specific.
 
Originally Posted By: MilesO
The only concern I have with that is.. does the multi-grade oil, say 5w-50wt, meet the weight criteria at the same temp as a single wt oil would ?

At operating temp (here assumed to be 212F), yes. But the advantage of multi-weight oil is that it will not thicken up as much as single weight when the temperature drops, and that's a good thing.

Anyway, what is the real reason you're asking the question? What is the actual problem that you're trying to cure?
 
Yes. A 10w-50 and a SAE 50 (monograde) will be in the same visc range @ 100C/212F. The difference would be in cold performance characteristics in terms of "apparent viscosity".

Beyond that, the multivisc oil will, without doubt, have VII (viscosity index improvers) that help the oil "appear" like a 50 weight @ 100C. As they shear, the oil reverts to it's core base stock viscosity. That won't happen with a monograde.

Let me try and give you an image. It's just an example and extremely simplistic and not entirely correct.

You take a base stock that has a sub 5.6 cST visc @ 100C ..and let's just say you called that 10W ..you then dope the oil with tons of VII polymers that allow it to simulate a 9.29cSt fluid @ 100C. So it would react/appear just like a 10weight @ some cold temp ..because that's exactly what it is. It will however "appear" like a much heavier fluid @ 100C THAN A 10WEIGHT WOULD @ 100C due to the polymers that are transparent at colder temps (coiled up) but make the fluid have a higher hot visc (uncoiled).
 
I have to move away from the computer for an hour or so . will revisit this post again 1800 EST.

Thanks to all for the replies, I am following your explanations and examples. I will explain the why of my question upon return.

Miles
 
I'm interested in what the viscosity vs. temperature trend looks like for, say, a 5w30 between 0F and 300F. Does anybody know where that can be found for any type/brand of oil?

K
 
Originally Posted By: Kaboomba
I'm interested in what the viscosity vs. temperature trend looks like for, say, a 5w30 between 0F and 300F. Does anybody know where that can be found for any type/brand of oil?

K


Using online viscosity calculators, you can. Just plug in the visco at 40C and 100C (and/or VI) from the spec sheet.
 
The Widman Viscosity Chart that Gary provided the link for answers the question but to put in layman's terms using Toyota's 0W-20 as an example.
It's vis falls in the 20wt range with oil temps from 92C to 121C
It's equivalent to a 10wt from 122C to 141C
It's " to a 5wt above 141C
At colder temps
It is like a 30wt from 79C to 91C
It is like a 40wt from 68C to 78C
It is like a 50wt from 57C to 67C
It is like a 60wt from 52C to 56c
It is like a 70wt from 45C to 51C

Heavier grades SAE grades will of course have proportionately different ranges but you get the idea.
 
In general, , I have found the change to be linear.
No great shifts or surprises from 0 deg F to 212 deg F.
A simple graph of temp/viscosity will give you your approximations.
 
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