Viscocity rating @ 40 C

bonjo

all PDS I have come across give viscocity value @ 100C and most at 40C as well.

While I can relate to the 100C measurement when engines normally run between 80~90 degC (from my experience), I do not see the merits of measuring the viscocity at 40C!

Perhaps one measured at 0C would be of better value.

So what is the wisdon behing the 40C??

Peruse the SAE J300 chart and read a bit about kinematic and dynamic viscosities. You'll see that differing viscosity grades are graded at different viscosities . The 100ºC and 40ºC is simply a standard. There are MRV and CCS ratings that cover differing aspects of how a lubricant performs at specified cold temperatures.

There's much more to it and just the 40 and 100.

40C is a standard that's been used for gear and hydraulic oils forever, since it's closer to the operating temperature of oils run at in many machines.

KV40 serves as a data point. It gives you a plot of viscosity increase with temperature drop so you can determine the viscosity index.

It's also an important spec for certain racing engines, particularly drag racing.

KV40 serves as a data point. It gives you a plot of viscosity increase with temperature drop so you can determine the viscosity index.
Are you able to show or explain how that's done? Thanks!

I do not see the merits of measuring the viscocity at 40C!

Perhaps one measured at 0C would be of better value.

You never started an engine at 40°C in the UK, for example during summer?
Your engine jumps instantly from 0°C to 100°C? It reaches 100°C in shorter
distances? Your transmission (the same applies) runs at 100°C? Actually very
most transmissions won't ever reach 100°C at all.

ps
Modern engines use to run in the range of 100 and 110°C for both coolant
and oil at least during spring, summer and autumn/fall.
.

Are you able to show or explain how that's done? Thanks!

This makes no sense to me ... AGMA, Sayboldt, SUS ... ??? I am ignorant of all this. It's like a foreign language to me.

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i had seen a great article + graphs of how oils are effected by temps on machinerylubrication.com + i will never forget BUT cant find it as it showed how much faster non REAL synthetics thickened in the cold + thinned but not as drastically in heat. remember reading that NHRA pro stockers that use very thin oils do NOT heat up enough to reach a 100C spec. might have been from HPL as they do many pro racers

This makes no sense to me ... AGMA, Sayboldt, SUS ... ??? I am ignorant of all this. It's like a foreign language to me.

Sorry. I tried a Google search

Sorry. I tried a Google search
I appreciate the effort ... should have said so earlier. Sorry.
Do you understand the chart and the acronyms and terminology?

I do not agree with oil & coolant running at 100~110C. This is when the electric fans kick in and thermostats open at 80~90C. Oil temps are also 80~90 @ working temps.

From my understanding, the highest engine wear is from a cold start. Lubrication being a critical factor. I consider 40C, being a warm engine (albeit not workig temp).
For me, the oil PDS (available to the public) would be more meaninful if it showd viscocity at "0"C or even "10" instead of 40

This makes no sense to me ... AGMA, Sayboldt, SUS ... ??? I am ignorant of all this. It's like a foreign language to me.

AGMA is the American Gear Manufacturers Association. Generally no longer relevant. Also, not relevant in Automotive application at all.

SUS or Saybolt Universal Viscosity is another standardized test procedure measuring Kinematic viscosity. Also, no longer really utilized widely.

SAE - Society of Automotive Engineers - there are two sections - Engine oil (Self explanatory) and Gear oils - this grade of gear oil is only for Automotive usage.

ISO - International Organization for Standardization - No, it is not International Standards Organization. That is a question on the STLE exam.

ISO and AGMA grades are based at 40C tests for viscosity.
SAE Engine oils and gear oils are based on 100C for their viscosity testing.
One of the major reasons for testing an engine oil at 40C is to determine what it viscosity it is for ISO.

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ISO - International Organization for Standards - No, it is not International Standards Organization. That is a question on the STLE exam.
OK, I just had to know...

OK, I just had to know...

View attachment 132134

Yup. The Acronym doesn't line up with the name. From what I was told, the big fit was being thrown by Russians during the naming process of it.

Kind of like UTC which stands for Universal Coordinated Time and not Universal Time Coordinated. It's a trick question on a FCC exam.

I am about to order a UOA kit from Millers oil. Their technicians (over here at least) are very friendly & happy to talk technical.
I will also ask them this question as they quote Kinematic Viscosity at 40°C.
Incidently has wwnyone used their kit

Are you able to show or explain how that's done? Thanks!
Viscosity at 40C and 100C is used to calculate the Viscosity Index. That's why oil spec sheets show KV40 along with KV100.

The 40 degree viscosity value is very important to me. I want it as low as possible. If it is in the 40cS range then I know I can rev up faster here in Florida. As it turns out as I leave my neighborhood I immediately jump onto a road with a speed limit of 55 MPH so I often need to "gun" it. There is no time to warm up the oil at all.

Ali

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