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What are the lower and upper limits of viscosity at which 15W40 Engine oil must be rejected - will anybody clarify?

What is the difference between kinematic viscosity and absolute viscosity, which one should be taken into consideration for determining whether used oil is suitable for furthe use or not?
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Hi we are fortunate enough to be monitoring 30 large Compression ignition rail engines and 20+ large spark ignition gas engines,
the no go used by these engine owners is +/- 10% original spec, this may be a bit conservative but there has never any outrage using this spec,
As to which system to measure with we use an external lab so our experience is not so good in this area although kinematic shears the fluid so would that could be best,

hope of this is of use and maybe other can fill in the gaps,

Regards Rob S
SAE has given the lower and upper limits as 12.50 cSt minimum and 16.30 cSt maximum for the 15w40 oil grades. Also as per the ASTM D6224 warning level for in-service engine oils the limit is given as plus or minus 10% of the new oil.The Kinematic Viscosity is the fluids resistence to flow under gravity at specified conditions.While Absolute Viscosity is the product of Kinematic Viscosity and density of that oil.
How noted Mr. Menon the SAE J300 defines the SAE 15w-40 between 12.5 cSt and 16.30 cSt. All oils with KV @ 100 °C may considered as SAE 40 (note pls not SAE 15W-40, but SAE 40 only. For spec 15W this oil must meet low temperatures properties - Cranking Viscosity not above 7.000 cP @ -20 °C and Pumping Viscosity not above 60.000 cP @ -25 °C). As in UOA for Engine Oils usually use the measure of KV@100 °C we will speak about SAE 40.
So, if you have any engine oil with spec SAE 15W-40, this oil MUST have KV@100 °C between 12.5 to 16.3 cSt. Let us assume that your oil have boundary KV 12.5 cSt. In this case the lower rejected limit will be minus 10% (some persons establishes another values), i.e. 11.2 cSt. In other case your SAE 15W-40 oil may have another boundary KV@100 - 16.3 cSt. Then upper rejected limit will be 17.9 cSt (plus 10%). Thus, the formal answer on Prabhakar Agrawal’s question should be - from 11.2 to 17.6 cSt at 100 °C, what will be pure hokum.
It is obvious that for each specific fresh oil with specific KV@100 °C will be specific lower and upper limits, for example ±10%. Therefore in UOA very important to have information about FRESH OIL that used for lubricating your equipment. In this case it is not allowed profit by promise and information data which present in product description. It is needed exactly values for Lubricant, in our case it will be KV@100 °C.
I think that right answer on Prabhakar Agrawal’s question should beginning with counter-question: “What KV@100 °C for your fresh SAE 15W-40 oil?”
Excuse me for many words.
Hi Mr Mikhail,

Don't worry about your words.It is OK.You may please note Mr Prabhakar Agrawal's post ,he was looking for the rejection limits of a 15w40 oil.So anything below and beyond the above mentioned limit (12.30 cSt - 16.30 cSt) will surely change the grade to either 30 or 50.That means we can not call it as a 15w40 oil.The drain out limits will be different for different engines as per the engine manufactures recommendations.That is why CUMMINS has recommended a decrease of 1 SAE viscosity grade.Got it.
Kinematic viscosity can be followed for used oil analysis.

Viscosity rejection limits

@ 40'C + or - 25%
@ 100'C + or - 15%

quote:
Originally posted by Prabhakar Agrawal:
What are the lower and upper limits of viscosity at which 15W40 Engine oil must be rejected - will anybody clarify?

What is the difference between kinematic viscosity and absolute viscosity, which one should be taken into consideration for determining whether used oil is suitable for furthe use or not?

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