It appears that way.
Also 5W-20 is not thicker than 0W-20. It just has a different winter rating.
Why wouldn't a 5w50 be better than a 5w40?
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Also 5W-20 is not thicker than 0W-20. It just has a different winter rating.
Classic and widespread belief that a "5 weight 20" (sic) oil is thicker than a 0W-20. Can't stamp it out.
Agree! Pretty cool name and what a grade. I wonder what it looks like when you pour it.
edyvw
$50 site donor 2026
It is the dynamic viscosity measured using a cold cranking simulator. It is not Kinematic viscosity that is used to determine grade.
As explained, it guarantees you that oil will be pumpable at -30 in the case of 5W or -35 in the case of 0W.
There is also a pour point that plays the role in very cold scenarios, but that is a really non-scientific way to determine cold performance. But, for example, if I were living in Fairbanks, AK, besides 0W, I would make sure the oil I use also has a pour point as low as possible, which also indicates a lot of PAO in the oil.
As for 5W50, there are numerous reasons why 5W50 is not a preferred oil.
1. 5W50 has a lot of VI. It will shear down fairly fast in most oils (some, Motul 300V, Redline 5W50, HPL are a different story).
However, manufacturers who make vehicles that need that grade probably want high HTHS more common in very good 5W40 oils, around 4cP. Because 5W50 will have HTHS around 4cP, it is safe to assume that regardless of shear, HTHS will stay high enough, probably 3.7cP and higher. They are assuming the owner will just buy average oil, so they push the grade. This is why approvals matter in Euro vehicles, because you know you are buying oil that has to meet a certain standard (does not mean there are no better oils, even if approved for the same standard).
For example, BMW used 10W60 in some M engines. In reality, after 5-7.5K, and definitely at 10K, those oils would shear down to thick W40. Using some extremely stout 5W50 or 10W50 like HPL, etc., means over OCI they stay in grade because. base stocks etc.
2. Power. Higher HTHS, more resistance = more heat.
3. Fuel efficiency: Higher HTHS=lower mpg.
As others have described, the W grade is related to a maximum viscosity at a specific temperature. It's all detailed in SAE J300 shown below. In order for an oil to meet a minimum W grade rating, it must pass both the Cold Cranking and Pumpability dynamic viscosity (units of cP) requirements shown in the table. You don't know the temperature aspect unless you look at the table.
Probably cost/quart for 40 weights, and availability. It is not that difficult to find a 0W-40 Euro oil on the shelf; it usually costs less than the Euro 50 weights and I would be willing to bet the wear metals on a UOA are about the same between the two. Just an opinion though, everybody has one.
In my experience, all 0-weights do not flow the same. For example, 0W30 will be thinner than cold than a 0W40, which will be thinner when cold than a 0W50. So while you might be thinking that all three of those oils will flow equally well when cold, that is definitely not the case. Then there's stuff like Mobil 1 European Car 0W40, which is thicker when cold than Mobil 1 Euro 5w40 according to the Mobil 1 spec sheet.
I was running Mobil 1 5W40 Euro in my '02 Porsche 911 Carrera, and my '11 Audi S4. I switched both of them to Mobil 1 5W50--the 911 because Porsche said that 5W50 was officially approved for use in the M96 engine, and the S4 because it likes to run its oil hot--cruising down the interstate at 85mph results in oil temps in the 240 range, which is apparently normal, but seems toasty. After switching to the 5W50, the 911 would occasionally exhibit an unfriendly tapping for a couple seconds on cold start, and the S4 would have a few seconds of cam chain rattle. I ran both cars on 5W50 for about 1000 miles, then switched back to the 5W40 and the noises went away. I read up on the 5W50, and it's actually more like a 15W50 when cold--no wonder it didn't flow as well as the 5W40.
I was running Mobil 1 5W40 Euro in my '02 Porsche 911 Carrera, and my '11 Audi S4. I switched both of them to Mobil 1 5W50--the 911 because Porsche said that 5W50 was officially approved for use in the M96 engine, and the S4 because it likes to run its oil hot--cruising down the interstate at 85mph results in oil temps in the 240 range, which is apparently normal, but seems toasty. After switching to the 5W50, the 911 would occasionally exhibit an unfriendly tapping for a couple seconds on cold start, and the S4 would have a few seconds of cam chain rattle. I ran both cars on 5W50 for about 1000 miles, then switched back to the 5W40 and the noises went away. I read up on the 5W50, and it's actually more like a 15W50 when cold--no wonder it didn't flow as well as the 5W40.
What does it mean:
"Severely refined petroleum distillates"
Is it Group III or Group II oil?
Tight bearings can operate fine on thicker oil and even benefit from a thicker viscosity resulting in more film thickness (why many people go up a grade), but looser bearings are much more sensitive to thinner oil.
The W grade rating per SAE J300 is just defining a max dynamic viscosity allowed at a certain temperature, so there can be a lot of wiggle room within a W grade range. To compare the same W grade, you would have to compare the exact Cold Cranking viscosity of each oil at the -35 C test point in the case of a 0W grade.
Where can we see those or you are comparing their KV at 40°C?
Also, at what temp. were/are your cold starts?
Why did you consider Mobil 1 5W-40 over 0W-40?
Thanks for the shared information.
No clue at all, I didn't look into it beyond confirming it's apparently a real product. My only use for such a thing would be like I said, put on the wall as shop art.
I do we need to?
There is a number associated with the CCS. So if one of two oils rated 0W or 5W has higher number at the low temp. ( at -30°C or -35°C) that means that oil is ticker than the other one, regardless both are rated as 0W or 5W oils.
I thank everyone for their info... I am now MORE confused...
So the number before the W in no way reflects how thick the oil is at room temp???? I understand that the rating is based on flow at -30 degrees to meet the definition of the rating. But how would that inherent viscosity at -30 NOT effect the viscosity art room temp? Inherently, looking at a 0W oil, and a 10w oil in my garage, at room temp, there is a world of difference! Ditto a 20w50...
Are you folks saying a 0w40, can have the SAME or better/THICKER viscosity all the way from -35 to at least room temp, than a 5w40 or 10w40? The only difference is the 0w40 has a pourability down to a lower temp?
So If I wanted to know which oil had a greater viscosity compared to another, at room temp, what number am I looking at?
So the number before the W in no way reflects how thick the oil is at room temp???? I understand that the rating is based on flow at -30 degrees to meet the definition of the rating. But how would that inherent viscosity at -30 NOT effect the viscosity art room temp? Inherently, looking at a 0W oil, and a 10w oil in my garage, at room temp, there is a world of difference! Ditto a 20w50...
Are you folks saying a 0w40, can have the SAME or better/THICKER viscosity all the way from -35 to at least room temp, than a 5w40 or 10w40? The only difference is the 0w40 has a pourability down to a lower temp?
So If I wanted to know which oil had a greater viscosity compared to another, at room temp, what number am I looking at?
Patman
Staff member
If you look at the viscosity at 40C that gives you a little bit of an idea of how one oil compares to another. On a very hot summer day in some of the southern states your oil could be at or just below 40C on the first start of the day.
Yes, but within a W grade (say 0W) if you compare the actually CC dynamic viscosity to other 0W grade oils, one 0W can be thicker at -35C than another 0W. That's what I'm talking about in post 52. The W grade can be a range where not every 0W has the same exact CC viscosity at -35 C. That's why someone might find that not all 0W grade oil crank the same way in the same engine at the same temperature.
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Please try to read and comprehend the explanations already given.
How the oil viscosity behaves from say -30C to room temperature can be dependent on the base oil and the amount and type of VIIs used in the formulation. That's also true when comparing the KV100 (like the Project Farm cold oil flow "pour point" races) to a dynamic viscosity when cold, which is what the Cold Cranking and Pumpabilty viscosity are.
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