Synthetic vs. Dino and W Ratings

[dsmith41]

It is well known that synthetic lubricants offer much better protection in cold conditions compared to dino oils. But what if they have the same winter rating? If you have a 5w-30 synthetic oil and a 5w-30 dino oil, why is the dino oil allowed to be much more viscous at, say, 0 degrees F?

Is there just that much range within the winter ratings? Just like GC is a thick 30 weight and Edge is a thin 30 weight but they are both 30 weights?

I know cold pumping viscosity is more important to look at for a cold weather oil but since oil companies don't publish that on the bottle and it can sometimes be hard to find it online even, what do the winter ratings really tell you about an oil?

 

[bepperb]

Well, the winter ratings are done at a different temperature for each rating. And to be honest, they're not that low. IIRC, they're in the 0 to 20 degree range.

If you go to the Widman oil visc graphing site, and enter the data for say Mobil 5000 5-20 and M1 5-20, you'll see very little difference and little space between the lines (though the syn is favored) but a huge difference between the 5-20 and 5-30's. But, the pour point for Mobil 5-20 5000 is in the -20's, whereas M1 5-20 is in the -40's.

So, very little. Honestly, I think M1 10-30 would pass as a 5-20 based on what you can extrapolate from the 40, 100 cst and VI. But say it did, they'd still want to sell a 10-30 for the buying public who preferred that "grade".

 

[mechtech2]

Yes, there is a range for oil viscosity number specs.
Thickness at 0 deg F,and 212 F ,correspond to the first and last numbers of a multiweight oil.
From what I have gathered, it is when it gets much below 0F that the synthetic will usually not thicken as much as the dino, and be superior. But at the rated spec, both will be in their range.

 

[dnewton3]

The disparty of viscosity is not very evident at zero, and not really at all at +20F. The advantage to synthetics happens at much, much lower temps (well into negative F temps ).

Which is why that claimed "advantage" is a waste of expenditure for most of us. We just don't see e-x-t-r-e-m-e temps that call for such capability. This disparity isn't justified for most people. We think it's cold because out bodies tell us it's not comfortable. But today's 5w-20 lubes are very capable fluids at low temps, even in dino form.

If one were to experience -20F on a routine basis, then I'd say a quality synthetic would be worth the money. But that's not what most of us have happen. We just want the "best", even when there is no "need" for such product.

 

[bepperb]

So Pablo's table translated into Fahrenheit for us Neanderthals:

10w -13 degrees
5w -22 degrees
0w -31 degrees Fahrenheit

but to make this even more confusing, the 0w needs to pass at a lower pressure than the 5w (even at the colder temp) and the 5w lower than the 10w, so the difference is even larger than it would seem from just looking at the temps.

Perhaps this is why there aren't any dino 0w oils, since most 5w-20 and 5w-30's have pour points above -31???

 

[mechtech2]

It is evident from Pablo's chart ^^ that there are additional specs for the first number in a multigrade oil.
It is not only is the 0 deg F that is considered.
The viscosity at temperatures way below that goes along with it.