Oil grade vs engine temp

[Quattro Pete]

Originally Posted By: Yannick
Is the Oil viscosity thicker when engine is hot? (5w30). or viscosity never change is the oil property change ? I want to know what means 5 (cold) w 30 (hot) with simple explanation.

5w means that the oil was tested to have cold cranking viscosity of less than 6,600 cP at a temperature of -30 Celsius but more than 6,200 cP at a temperature of -35 Celsius.

30 means the oil was tested to have kinematic viscosity of between 9.3 and 12.5 cSt at a temperature of 100 Celsius.

That is all it means.

Also, every oil is always thinner when hot. Always.

http://www.widman.biz/English/Tables/J300.html


EDIT: Bah, OVERKILL beat me to it, once again.

 

[ARB1977]

Who knows if the water temp is up to full temp once the needle stops.

 

[Quattro Pete]

Originally Posted By: ARB1977
Who knows if the water temp is up to full temp once the needle stops.

It's not.

But even if it was, that still does not tell you much about the oil temp itself.

 

[00Max00]

Originally Posted By: OVERKILL
Originally Posted By: Yannick
Quick & easy one here ;

5w30 , 5 is the grade when oil is cold (thinner). 30 is the grade (thicker) when oil is hot.

Can we say when the engine temp gage(not the oil temp gage) is locate to its normal level when running the oil is now at 30grade? Engine temp gage is reading the prestone temp I think ,and not the engine (oil) temp. At then end when the engine get the 30grade oil ?
I hope you understand my question.
thanks


I'm just going to quote myself from another thread here where I believe I explained it quite well:

Missing are the new SAE 16 and 12 grades due to the date of the post.

Original discussion here:
https://bobistheoilguy.com/forums/ubbthreads.php/topics/3515622/Oil_change_question


The number in front of the W is not a representation of an SAE 5 "when cold", which doesn't exist as a motor oil grade, neither does a 10 or a 15, all of which are a xW classifications. The same goes for a 0. Is there an SAE 0? No. The SAE grading system for oils under the non-W classification starts at SAE 20.

Just as an example here, Mobil 1 0w-40 and Mobil 1 0w-20 both carry the 0w designation. Which means they meet the cold temperature performance requirements for that classification. This classification is simply a set of limits for MAXIMUM viscosity at -40C and -35C respectively. That is the ONLY thing those two oils have in common:

M1 0w-20:
Visc@100C: 8.7cSt
Visc@ 40C: 44.8cSt
MRV@ -40C: 9,200cP

M1 0w-40:
Visc@100C: 13.5cSt
Visc@ 40C: 75.0cSt
MRV@ -40C: 31,000cP


Is 9,200cP close to 31,000cP? Nope. But they are both under 60,000cP at -40C (and under 6,200cP for CCS @ -35C), so they both get to carry the 0w designation. There is no temperature that M1 0w-40 is even CLOSE to the same viscosity as the 0w-20.

You'll notice the 0W and 5W designations have the exact same visc minimums @ 100C, with no maximums for 100C or HTHS. You'll also notice the distinct absence of an SAE 5, 10 and 15 grade on the chart

Those grades only exist as ISO hydraulic oil grades, not engine oils.

Does this mean 0W40 is thinner at 0 C than 5W30?

 

[Shannow]

Originally Posted By: 00Max00
Does this mean 0W40 is thinner at 0 C than 5W30?


Not at all.

Take Mobil's 0W30 and 5W30, they are virtually the same at 0C...the 0W40 is thicker then either.

 

[Merkava_4]

5w30 is SAE 5 when cold and SAE 30 when hot.

 

[Quattro Pete]

Originally Posted By: Merkava_4
5w30 is SAE 5 when cold and SAE 30 when hot.

No, it isn't. Try reading what OVERKILL posted above.

 

[aquariuscsm]

I had someone here say one time that for instance a 10W30 is basically a 40 wt oil when cold and a 30 wt when hot. But someone else chimed in and said that's not entirely accurate.

 

[Merkava_4]

Originally Posted By: Quattro Pete
No, it isn't. Try reading what OVERKILL posted above.


It may not be the correct answer, but it's sure as heck easier to understand!

 

[Quattro Pete]

Originally Posted By: Merkava_4
It may not be the correct answer, but it's sure as heck easier to understand!

That's the spirit.

 

[OVERKILL]

Originally Posted By: Merkava_4
5w30 is SAE 5 when cold and SAE 30 when hot.


I see you are really on the ball with reading comprehension today, LOL!

 

[OVERKILL]

Originally Posted By: aquariuscsm
I had someone here say one time that for instance a 10W30 is basically a 40 wt oil when cold and a 30 wt when hot. But someone else chimed in and said that's not entirely accurate.


Because it's not accurate. Read what I posted above. It isn't difficult to understand if you can picture it in your head.

 

[00Max00]

Originally Posted By: Shannow
Originally Posted By: 00Max00
Does this mean 0W40 is thinner at 0 C than 5W30?


Not at all.

Take Mobil's 0W30 and 5W30, they are virtually the same at 0C...the 0W40 is thicker then either.


Then what makes the 0W30 a 0W, and 5W30 a 5W if they are the same at low temps? Don't you think if 0W40 is thicker than a 5W30 at low temps, doesn't this make it to be more link a 10W40?

 

[Shannow]

Originally Posted By: 00Max00
Originally Posted By: Shannow
Originally Posted By: 00Max00
Does this mean 0W40 is thinner at 0 C than 5W30?


Not at all.

Take Mobil's 0W30 and 5W30, they are virtually the same at 0C...the 0W40 is thicker then either.


Then what makes the 0W30 a 0W, and 5W30 a 5W if they are the same at low temps? Don't you think if 0W40 is thicker than a 5W30 at low temps, doesn't this make it to be more link a 10W40?


No, the "0W", and the "5W" are how the lubricants pum at temperatures like -40 and -35C respectively.

The bit about "better flow at start-up", at "normal" temperatures is a BITOG myth....unless of course your "normal" is 20-40 below 0C.

 

[OVERKILL]

Originally Posted By: 00Max00
Originally Posted By: Shannow
Originally Posted By: 00Max00
Does this mean 0W40 is thinner at 0 C than 5W30?


Not at all.

Take Mobil's 0W30 and 5W30, they are virtually the same at 0C...the 0W40 is thicker then either.


Then what makes the 0W30 a 0W, and 5W30 a 5W if they are the same at low temps? Don't you think if 0W40 is thicker than a 5W30 at low temps, doesn't this make it to be more link a 10W40?


It is explained in my earlier post. Go back and re-read it until it makes sense

 

[Pontual]

And what's wrong with my explanation? It's a 5 that won't thin out as much, hahahaha. Look there.