Any reason to choose 5W over 0W oil?

[TopPhrenologist]

I just picked up a 2023 6.7 Powerstroke diesel and am trying to learn as much as possible to keep this engine a long, long time. I live in a northern state where temperatures below 0F are common in winter, but it's exceptionally rare to see temperatures below -20F. The user manual states that 5W-40 oil should be used when the lowest temperature you see is -20F.

Assume both oils cost the same or assume that I don't care how much they cost, is there a reason why I shouldn't just use 0W-40 and never worry about how cold it is? Is there a reason why someone in a warmer climate should not choose 0W oil (again, aside from cost)? My understanding is that 0W would help reduce wear during initial startup even if it's not freezing outside because it's the same viscosity it would be at operating temperature.

 

[OLEJOE]

Availability is the limiting factor for us in the South. If you are in the northern area where 104-110 isn’t an issue I wouldn’t think it would hurt and could possibly help where it does get below 0. If it gets down into the teens here it only lasts for a couple of days and normally around 32 for lows. We would have to order 0w-40 around here.

 

[userfriendly]

Delvac 0W40. Nothing better for cold starts on those mornings you would rather stay in bed.

 

[wpod]

The 5W vs the 0w is the cold cranking temps which is about 5* colder[ + or -].

 

[DemoFly]

0W has more viscosity improver, which makes it less shear stable. At the end of the oil change interval, the 0W-40 will be thinner than the 5W-40. It may (or may not) be a significant difference.

If you think you need a 0W-40 for winter, steer your mind to a block heater. Because cold starting in -20F with a 0W-40 without a block heater is still not ideal.

 

[TopPhrenologist]

0W has more viscosity improver, which makes it less shear stable. At the end of the oil change interval, the 0W-40 will be thinner than the 5W-40. It may (or may not) be a significant difference.

If you think you need a 0W-40 for winter, steer your mind to a block heater. Because cold starting in -20F with a 0W-40 without a block heater is still not ideal.

Totally understand about the block heater. I have one and I plan on using it.

Your comment about 0W being less shear stable is really what I was trying to get at. Does that mean that over time the 0W-40 oil will start to behave like a 5W or 10W-30? I assume it's not quite that simple...

 

[DemoFly]

Totally understand about the block heater. I have one and I plan on using it.

Your comment about 0W being less shear stable is really what I was trying to get at. Does that mean that over time the 0W-40 oil will start to behave like a 5W or 10W-30? I assume it's not quite that simple...

Yes it's likely for a 0W-40 to shear to the high end of a 30 grade within an oil change interval. A lower VII (Viscosity Index Improver) oil will also typically have a higher HTHS.

You can search VII on this forum and go down a rabbit hole. But my opinion is that 0W-40 type oils are only great when put in applications that spec either a 30 or 40 grade oil (like most euro gas and diesels).

If your truck were my truck I'd run Rotella T6 or Valvoline Premium Blue year round

 

[BornSlippy]

If your plugging the truck in on those cold nights anyway, I'd stick to the 5W-40.

 

[SC Maintenance]

I went down the vii rabbit hole. Of course my knowledge to start was zero and my knowledge at the end was confusion

The more or less conclusion I came to is there is no reason to use a lower cold weather rating than is needed due to the VII, but in the end if your running shorter OCI's then it likely doesn't matter. You also never really know how much VII any particular formulation actually has - your estimating based on rules of thumb.

If it were me I would likely get a block heater and just run the 5W-40.

 

[userfriendly]

Totally understand about the block heater. I have one and I plan on using it.

Your comment about 0W being less shear stable is really what I was trying to get at. Does that mean that over time the 0W-40 oil will start to behave like a 5W or 10W-30? I assume it's not quite that simple...

The CK-4 approval carries a stay in grade component. A 0W40 may have more “VM” than a 5W40, 10W40 or 15W40, but the VM will be less efficient. Meaning that it will not produce as much viscosity thickening as a more efficient viscosity modifier.
The less efficient VMs are more shear resistant and more of the product must be used to obtain the desired viscosity improvement.
VMs are expensive, so adding more of a less efficient VM will add to the cost of the lubricant.

 

[#18FAN]

HPL Cold Climate 5w40 would be a great fit ran it in a 21 6.7l Cummins-20F starts unaided very sheer stable oil. The oil was run year round.

 

[Snagglefoot]

Here is the Shell Rotella option. The Shell website describes it as CJ-4 but it might be CK-4 by now. Minus 20 F is not a big deal. If it were -40 I would recommend the 0w40. 5w40 would be fine at -20 F.

 

[kschachn]

Your comment about 0W being less shear stable is really what I was trying to get at. Does that mean that over time the 0W-40 oil will start to behave like a 5W or 10W-30? I assume it's not quite that simple...

Blanket statements are pretty useless here. The amount of VII required to achieve a particular winter rating is dependent on the specific base stocks used, and the shear stability of the VII is dependent on the specific VII molecules. Some are better than others.

Manufacturer approvals have shear stability requirements.

 

[Thermo1223]

Blanket statements are pretty useless here. The amount of VII required to achieve a particular winter rating is dependent on the specific base stocks used, and the shear stability of the VII is dependent on the specific VII molecules. Some are better than others.

Manufacturer approvals have shear stability requirements.

This, it's a also a bit OCD considering the difference again between 5 & 0 is almost immeasurable at the temp the OP might be operating at.

 

[ripcord]

This, it's a also a bit OCD considering the difference again between 5 & 0 is almost immeasurable at the temp the OP might be operating at.

Agreed, but pointing that out is like saying water is wet. This whole site is nothing but a safe outlet for directing our OCD (or CDO for some of us) tendencies.

 

[OVERKILL]

Blanket statements are pretty useless here. The amount of VII required to achieve a particular winter rating is dependent on the specific base stocks used, and the shear stability of the VII is dependent on the specific VII molecules. Some are better than others.

Manufacturer approvals have shear stability requirements.

Exactly. There's absolutely no guarantee that a 5W-40 will have less VII than a 0W-40, in fact, I believe I've posted an example previously of a 10W-40 having more VII than a PAO-based 0W-40.

 

[#18FAN]

Deleted post oops

 

[Thermo1223]

Agreed, but pointing that out is like saying water is wet. This whole site is nothing but a safe outlet for directing our OCD (or CDO for some of us) tendencies.

I'm going to need verified HTHS numbers for this "water" you speak of. Also is it good for a engine that calls for a 0w16 since it seems thin enough?

 

[930.engineering]

Does that mean that over time the 0W-40 oil will start to behave like a 5W or 10W-30? I assume it's not quite that simple...

Yes, not that simple. However while a 0W-40 may end with a 0W-30,
depending on base oil and VII used, it's less likely to end with a 5W.
With cold nights down to -20°F I'd probably use a 0W-40 or 0W-30.
.

 

[Redhawk454]

another thing to remember... oil stays up in the cylinder head for a long time...