If thick oil offers more protection, then isn't cold oil best?

[cheesepuffs2]

Reading comments here, it obviously comes up that thicker oil does a better job of separating two parts from contacting one another, which reduces wear. This is often stated as if "more is better" with no real cap on how thick is too thick until there are diminishing returns.

My thought (not my true belief) is this:

If thicker is always better until any circumstance, well, we know that a 5W-20 grade oil as say 5 degrees F is many times thicker than say a 5W-30 grade is at 212 degrees. Aside from the question of cold cranking, and assuming the oil pumps quickly enough to avoid damaging the engine since it is a 5W, then wouldn't a cold oil (that's still within temperature range for the grade) prevent wear the best, even better than nearly any oil at it's full operating temp?

 

[kschachn]

Keeping parts separated is the point. And yes, a thicker oil will do a better job of that under all circumstances.

But cold oil is not ideal for many reasons, some of which I'm pretty sure you already know in this thick vs. thin resuscitation.

Actually I think you already know the answer to your question in general.

 

[cheesepuffs2]

Keeping parts separated is the point. And yes, a thicker oil will do a better job of that under all circumstances.

To what end, though? If we created a hypothetical "40W-100" PCEO, at what thickness do the bearings end up becoming dams for the oil and causing such high dwell time that the heat generated becomes detrimental to either the oil or the materials it surrounds?

My point is that I read all the time here how "going thicker will never cause damage to an engine" but I don't see how that can be stated as an absolute with no ceiling. There has to be a point where the drawbacks outweigh to benefit. Imagine an oil as thick as molasses. Would that really provide more protection than a 30 grade if it can't flow freely through the bearings? It's "thick" though, so thick must mean good, right? At some point the bearin clearances won't be able to accommodate the viscosity.

 

[JavierH19]

Reading comments here, it obviously comes up that thicker oil does a better job of separating two parts from contacting one another, which reduces wear. This is often stated as if "more is better" with no real cap on how thick is too thick until there are diminishing returns.

My thought (not my true belief) is this:

If thicker is always better until any circumstance, well, we know that a 5W-20 grade oil as say 5 degrees F is many times thicker than say a 5W-30 grade is at 212 degrees. Aside from the question of cold cranking, and assuming the oil pumps quickly enough to avoid damaging the engine since it is a 5W, then wouldn't a cold oil (that's still within temperature range for the grade) prevent wear the best, even better than nearly any oil at it's full operating temp?

Where have you seen this?. I can't recall seeing anyone recommend anything beyond the usual 30 or 40 grade oil for a normal car. I usually state that going beyond these likely won't result in any additional protection but will only hurt fuel economy and that a 40 grade is thick enough for the vast majority of vehicles and peoples driving conditions. I don't see members telling others to go straight to 50 or 60 grade. Those are rarely recommended without a valid reason.

 

[cheesepuffs2]

Where have you seen this?. I can't recall seeing anyone recommend anything beyond the usual 30 or 40 grade oil for a normal car. I usually state that going beyond these likely won't result in any additional protection but will only hurt fuel economy and that a 40 grade is thick enough for the vast majority of vehicles and peoples driving conditions. I don't see members telling others to go straight to 50 or 60 grade. Those are rarely recommended without a valid reason.

I see it here all the time, including within threads on the first page right now. I'm not going to name and shame and use examples but they're everywhere and it's been repeated here for months. Not that people are saying "use a 60 grade" but that it gets stated like "no harm can come from using an oil that is too thick".

 

[CarlB]

Reading comments here, it obviously comes up that thicker oil does a better job of separating two parts from contacting one another, which reduces wear. This is often stated as if "more is better" with no real cap on how thick is too thick until there are diminishing returns.

My thought (not my true belief) is this:

If thicker is always better until any circumstance, well, we know that a 5W-20 grade oil as say 5 degrees F is many times thicker than say a 5W-30 grade is at 212 degrees. Aside from the question of cold cranking, and assuming the oil pumps quickly enough to avoid damaging the engine since it is a 5W, then wouldn't a cold oil (that's still within temperature range for the grade) prevent wear the best, even better than nearly any oil at it's full operating temp?

Let's assume what you are saying is true. What downsides could be caused by oil that is never at full operating temperature in an internal combustion engine?

Everything is about trade-offs.

 

[cheesepuffs2]

Let's assume what you are saying is true. What downsides could be caused by oil that is never at full operating temperature in an internal combustion engine?

Everything is about trade-offs.

This is veering away from my original topic, but to answer your question, excessive build-up of moisture and fuel, both of which are never a positive addition to any engine oil.

 

[Glenda W.]

Definitely points for creativity on another thick vs thin thread.

 

[TomYoung]

Reading comments here, it obviously comes up that thicker oil does a better job of separating two parts from contacting one another, which reduces wear. This is often stated as if "more is better" with no real cap on how thick is too thick until there are diminishing returns.

My thought (not my true belief) is this:

If thicker is always better until any circumstance, well, we know that a 5W-20 grade oil as say 5 degrees F is many times thicker than say a 5W-30 grade is at 212 degrees. Aside from the question of cold cranking, and assuming the oil pumps quickly enough to avoid damaging the engine since it is a 5W, then wouldn't a cold oil (that's still within temperature range for the grade) prevent wear the best, even better than nearly any oil at it's full operating temp?

The answer to your “question” is NO. The best protection is not provided by cold oil, and you are conflating the cold oil properties with the properties implied by the oil grade.

Also false is your characterization of the thick thin oil argument. Almost all oil is somewhere between 0w8 and 20w50, so there is an effective upper bound and a lower bound. You can freeze any oil until it is solid. No additional protection is inferred. If you are making some sarcastic comment on the thick/thin everlasting argument, so be it. Otherwise, consider that the fine oils available to us are technical, engineered products whose design allows great performance over time, satisfying multiple needs, including viscosity during cold starts

 

[JavierH19]

I see it here all the time, including within threads on the first page right now. I'm not going to name and shame and use examples but they're everywhere and it's been repeated here for months. Not that people are saying "use a 60 grade" but that it gets stated like "no harm can come from using an oil that is too thick".

There's no need to name or shame so I don't ask for that but at least post a few links to these examples. I'm usually see a 1 grade increase recommendation and sometimes 2 and rarely ever 3 or more.

I've posted owners manual sections that show Toyota allowing their vehicles to run on anything from 0w-20 to 20w-50, 0w-16 to 15w-40, and 0w-8 to 10w-30 and I never suggest the highest within those even though using 20w-50 instead of 0w-20 is not "too thick" as if it was "too thick" then Toyota simply wouldn't allow you use 20w-50 in the first place.

"too thick" from what I see is going over 2x typical hths. 0w-8 is typically 1.8 hths so 2x that is 3.6 hths which is a very thick 30 and that's all they allow. 0w-16 is typically 2.3 hths so 2x that is 4.6 hths which is a very thick 40 grade and that's all they allow. 0w-20 is typically 2.6 hths so 2x that is 5.2 hths which is also a very thick 50 and again that's all they allow and I agree with them. I don't think anything beyond any of those makes logical sense however I still don't think it will hurt anything even if you go beyond those high values as long as ambient temps permit.

I typically suggest at least going up 1 or even 2 grades within those ranges as insurance unless the vehicle is a lease that won't be getting bought out or it is owned but won't be owned long enough for it doesn't matter as some people want to own but only to the medium term of ownership being around 100k.

 

[kschachn]

No SAE grade is too thick as to cause damage. There are 70-grade oils used elsewhere in the world on a large variety of engines.

An improper winter rating can cause damage of course if it cannot be pumped. But if the oil pumps then it will lubricate. There is no arbitrary “only 2 grades higher” or any such restriction.

My Tiguan recommends a 20-grade oil. I have on occasion run a 50-grade to see how it affects consumption. No check engine lights, no sheared off oil pump sprocket, no glitter in the oil. It’s fine. Is it necessary? No. But that’s a lot different than the dire predictions sometimes made.

 

[4WD]

Definitely points for creativity on another thick vs thin thread.

Indeed - gonna stop and let the motor cool down more often

 

[Hohn]

Reading comments here, it obviously comes up that thicker oil does a better job of separating two parts from contacting one another, which reduces wear. This is often stated as if "more is better" with no real cap on how thick is too thick until there are diminishing returns.

My thought (not my true belief) is this:

If thicker is always better until any circumstance, well, we know that a 5W-20 grade oil as say 5 degrees F is many times thicker than say a 5W-30 grade is at 212 degrees. Aside from the question of cold cranking, and assuming the oil pumps quickly enough to avoid damaging the engine since it is a 5W, then wouldn't a cold oil (that's still within temperature range for the grade) prevent wear the best, even better than nearly any oil at it's full operating temp?

I think there's a bit of a misunderstanding. It's not the case that a thicker viscosity always reduces wear. If a film is present, there's no wear because there's no contact. As long as you are on the right side of the Stribeck curve and into full film lubrication, there is no contact and no wear.

Wear only results at mixed or boundary lubrication where actual surface contact can occur.

Being separated by a little or separated by a little more is still separated.

 

[ATex7239]

Yep, colder is better. Only doing short trips moving forward.

 

[kschachn]

I think there's a bit of a misunderstanding. It's not the case that a thicker viscosity always reduces wear. If a film is present, there's no wear because there's no contact. As long as you are on the right side of the Stribeck curve and into full film lubrication, there is no contact and no wear.

Wear only results at mixed or boundary lubrication where actual surface contact can occur.

Being separated by a little or separated by a little more is still separated.

There is never “no wear”. All oils produce wear at all times regardless of the film thickness. It’s just that catastrophic wear occurs when metal to metal contact occurs.

And HT/HS vs. wear graphs have been posted here that show a reduction in wear as the film thickness increases. But it is not linear and after a certain HT/HS the reduction becomes less and less.

 

[JAG]

All oils produce wear at all times regardless of the film thickness.

If two parts are not touching between two times due to being separated completely by an oil film, there is wear occurring? Let’s exclude corrosive wear or extremely minute removal of metal from oil flowing by.

To the OP, antiwear additives work more effectively at fully warmed up engine oil temperatures. Cold engine’s increased wear rates are generally mostly due to corrosive wear from water condensation and acids (per an SAE paper) and less effective antiwear additives.

 

[kschachn]

If two parts are not touching between two times due to being separated completely by an oil film, there is wear occurring? Let’s exclude corrosive wear or extremely minute removal of metal from oil flowing by.

Yes the fluid itself is abrasive and eventually causes wear as you note with flowing oil. But that’s small. Beyond that though there are always particles in the oil that cause additional wear especially without low micron bypass filtration. In fact this is the main source of wear unless metal-to metal contact is occurring.

The only wear-free bearings are vacuum bearings, but technically only in a perfect vacuum.

 

[JAG]

I see what you mean, kschachn. Reality is wild when one looks at it deeply enough.

 

[burbguy82]

Keeping parts separated is the point. And yes, a thicker oil will do a better job of that under all circumstances.

But cold oil is not ideal for many reasons, some of which I'm pretty sure you already know in this thick vs. thin resuscitation.

Actually I think you already know the answer to your question in general.

I think the issue here is the state of the engine when started.

Yes the oil is "cold" at startup, but it sure was not cold when it was shut off. Most of the oil is nearly gone from the affected surfaces, maybe and hour after shut down. The subsequent start, there is little oil to rely on.

Valve spring push pretty hard on a very small surface.

 

[TomYoung]

Definitely points for creativity on another thick vs thin thread.

I am at the point where I consider at least half of all posts to be crypto or blatant thick v thin discussions or provocations!