# Oil Viscocity confusion



## Nick2002GLI (Dec 23, 2008)

I have a question about oil viscosity... The oil weights range from 5-30, 5-40, 10-40, 10-30 and so on... They say that the 5w is the cold weight and it is supposedly thin when cold and it thickens up once the oil is hot... Well on the contrary, it seems to me when the oil is cold its like a thinner milk shake consistency, and when the oil is hot its almost like water... Aren't those claims a bit oxy-moronic??


----------



## AudiSportA4 (Mar 3, 2002)

Yes, the SAE system is confusing. 

It USED to mean that, in the example of 10w-40, the oil is a 40 weight at operating temp, but stays the same visc as a 10 (weight) oil would be at +32f. 

Obviously, the oil thins when hot and thickens when cold. 

The new SAE system is a series of "W" tests at correspondingly reduced temps. 

This article has the SAE J300 info... 

http://physics.info/viscosity/ 

...and a graphic... 









So, the label grade is the visc RANGE at operating temp, +100c. A 30 weight can be from 10-12cSt, 20 and 40 weight above and below that visc and so on. 

This graphic calc is very usefull, esp since you can input the data from any oil to compare to others... 

http://www.widman.biz/English/Calculators/Graph.html 

This is a fixed example...


----------



## TechMeister (Jan 7, 2008)

Nick2002GLI said:


> I have a question about oil viscosity... The oil weights range from 5-30, 5-40, 10-40, 10-30 and so on... They say that the 5w is the cold weight and it is supposedly thin when cold and it thickens up once the oil is hot... Well on the contrary, it seems to me when the oil is cold its like a thinner milk shake consistency, and when the oil is hot its almost like water... Aren't those claims a bit oxy-moronic??


 The link below may help you understand oil viscosity which is a flow rating of the oil at TWO different temperatures. 

http://www.kewengineering.co.uk/Auto_oils/oil_viscosity_explained.htm


----------



## AudiSportA4 (Mar 3, 2002)




----------



## jebglx (Jul 13, 2000)

knock it off you two :sly:


----------



## gehr (Jan 28, 2004)

jebglx said:


> knock it off you two :sly:


Are you AudiassA4 incognito?! or just his only friend! :laugh:


----------



## Gulfstream (Jul 28, 2010)

why are you guys so angry? Much better to focus on the facts and provide some useful info here instead, no ?


----------



## gehr (Jan 28, 2004)

Well yes and no!

I just think his black and white view of everything is demented, it's oil and he doesn't know anything over VW engineers........but thinks he does! It's just funny, sad but fuuny!:laugh:


----------



## Gulfstream (Jul 28, 2010)

everybody is different and entitled to their own opinions, lets not start another war over it 

:beer:


----------



## skier45 (Jul 27, 2009)

*viscosity*

how do they measure viscosity? i was always under the impression it was the size orface it would flow through at specified temperatures.


----------

