Kinematic viscosity how two ....

[Baveux]

How two oil like 5w40 and 5w30 can have such a widespread difference in spec a 40c ?

QS 5w40 euro is 80.8
PU 5w30 56.9

finally what that mean or what would be the difference when use in very cold climate , my understanding is a 5w is a 5w no matter what

 

[Greasymechtech]

QuakerState 5w50 96.1
Pennzoil 5w20 45.9

Most don't have a clue what the bottle label means..... "it acts like a 5 when cold and a 30 when hot" is the best that the consumer can say and is false and means NOTHING, but is all that many think and for obvious reasons.... brainless MARKETING and for the sake simplicity.

Below is the prefix/suffix SAE grading system. There are also non-SAE grades that some blenders use(and need to define).
An oil can be a single prefix, or single suffix only, or a multgrade with 1 prefix and 1 suffix, to help prevent consumer confusion. So, you won't see anymore 0w5w10w15w-30 oils or 0w-16,20 or 5w-16,20 oils. So, my SAE30/10w30 VPracing small engine oil is incorrectly labelled.

Both thick or thin 'labelled' oils can pass the 5w grade but I promise you that a 5w50 is going to considerably thicker than a 5w20 when cold. Years ago, some of the boutique oil brand provides viscosity curves for their grades. I didn't save the pamphlets but seeing the curves, at various temps, made you wonder what SAE was thinking and can improve upon. To SAE, the 40 degree viscosity measurement is meaningless and useless for their grading system.

 

[JavierH19]

Here's a small video. It shows the difference between many oils but I'd focus on the 5w-30 A3/B4 euro and 0w-40. It's at 20c first and -25c. The 5w-30 is slightly thinner when warm at 20c but in the -25c cold the 0w-40 is slightly thinner. But I'd agree that it's confusing and i don't blame you as it's never the same with all oils in a grade. You can have a 0w-40 that outperforms a 5w-30 in both cold and hot temps depending on the base oil.

 

[ZeeOSix]

... my understanding is a 5w is a 5w no matter what

The "W" rating is a cold use temperature limit based on cold cranking and pumpability viscosity ... it doesn't mean the cold viscosity is the same between all 5W oils.

 

[FCD]

The "W" rating is a cold use temperature limit based on cold cranking and pumpability viscosity ... it doesn't mean the cold viscosity is the same between all 5W oils.

Exactly, for example a 5W-50 is usually more viscous at 40c than a 10W-40.

 

[Baveux]

So what purpose serve the 5w ?

 

[wpod]

The "W" rating is a cold use temperature limit based on cold cranking and pumpability viscosity ... it doesn't mean the cold viscosity is the same between all 5W oils.

But the 5W oils meet the 5W spec.

 

[ZeeOSix]

But the 5W oils meet the 5W spec.

True, but their viscosity isn't always the same at the same temperature - that was the point.

5W oil #1 may not crank as well as 5W oil #2. Oil #2 could have a CC viscosiy close to a 10W, and oil #1 closer to a 0W ... but both are rated per J300 as a "5W".

 

[Bill_W]

So what purpose serve the 5w ?

In the case of 5w20 vs 0w20 of the same oil and the 0w20 needs VII the 5w20 would not need as much if not any. Also the base oil would be higher cSt in the 5w20. (of the same oil)

 

[OVERKILL]

In the case of 5w20 vs 0w20 of the same oil and the 0w20 needs VII the 5w20 would not need as much if not any. Also the base oil would be higher cSt in the 5w20. (of the same oil)

But that's not necessarily how they are blended, or typically, if we are talking about readily available oils, which all employ VII. If you give any credence to the calculations made on this subject there are many 0W-20's with lower VII content than many of the 5W-20's.

The base oil blend for a 0W-20 may be completely different from a 5W-20 for example, employing PAO where the 5W-20 has none. This has an obvious effect on VII content requirements. This is well evidenced by the Mobil SDS sheets that showed as much.

 

[Baveux]

can you feel the difference between the oil of the same visc at cold start up , I personally dont think so , the engine internal maybe, but enough to make a difference in the life of the car .... dont think so....im back to what we read often here.... buy whats on sale period

 

[ZeeOSix]

can you feel the difference between the oil of the same visc at cold start up , I personally dont think so ...

If one 5W has a CC viscosity close to breaking into the 0W range, and another 5W has a CC viscosity that's almost in the 10W range, then you would most likely detect a difference in the way the engine cranks over and starts when it's very cold outside.

 

[Baveux]

If one 5W has a CC viscosity close to breaking into the 0W range, and another 5W has a CC viscosity that's almost in the 10W range, then you would most likely detect a difference in the way the engine cranks over and starts when it's very cold outside.

Well yeah you remind me the day I started using synthetic many years ago, the cold cranking was obviously easier between the 5w regular and the 5w synthetic