"Nooks and Crannies" thin oil guys...

[BuickGN]

Originally Posted By: Gary Allan
I'm not saying a millisecond is so important. I do know that your 15w-50 will not be pumping instantaneously when you're visiting your pal in Frostbite Falls in winter. It also may not amount to much in terms of wear in the big picture.

The pump will be in relief whenever it can't move the mass that it has in front of it. Stuff the filter with chassis grease to demonstrate the process.

Cars used to stall a few times in winter before they had good enough oil flow to stay running. Naturally, that was at the high cold idle level of our choked carbs.


Of course, I wouldn't recommend 15w-50 in a cold winter.

I was thinking of the first second or so of startup, not referring to your post but there has to be that first instant of movement before the pump has a chance to bypass that it gets the heavy column of oil moving quickly. I quoted you but I was referring to someone else.

 

[Gary Allan]

yeah, I went out there. At worst I would imagine a shock bump of the gelatin/tooth paste ..but there's no real telling when/where the internal oil pump restrictions, coupled with the length and pump head, are going to allow the pump to divorce itself from the continuous fluid train. You can have a stationary Bay of Fundy at high tide.

 

[il_signore97]

We all have very good points, and the discussion has been good so far. But I don't think the thick/thin debate will ever have a definitive answer, nor should it.

I think we can all agree that a statement like "thick oil protects better than thin oil" is just as dumb as the "5W20 is recommended for all conditions / all temps / all places / all the time".

I do believe there is merit to the arguments presented by both parties here, but I also think that usage should play a strong role in lubricant selection.

Like BuickGN said, he regularly drives longer distances, highway miles, some climbing, pushing the car occasionally. He lives in California. Why not use ACD? Probably a good choice. I for one am a fan of a higher HTHS when the car is mostly highway driven, and will be pushed hard (even if only on occasion).

As he also mentioned, we are not sure why the 80% start-up wear occurs, and it may not have much to do with thick or thin oil. As long as the oil is flowing, I don't believe there is much to be gained from moving thinner. Just don't push the car too far up the RPM range until warm, or cavitation / oil starvation can and does occur (common sense to most of us I think).

For others who primarily do a lot of very short trips in cold weather, a higher HTHS may not help them. A thicker oil film (already too thick to begin with) is likely not useful to them. All of the cold starts over and over again in frigid weather would most certainly take their toll on the engine. Maybe in this case a 0W20 would be the best. It might not help *much*, but might be better than a 5W30 dino.

Then of course, what about the person that frequently starts their engine in cold weather but also pushes the car hard when warm? With all of the lubrication technology available today, wouldn't a robust syn 0W40 fit the bill perfectly?

Just adding a twist to the discussion!

 

[ekpolk]

Originally Posted By: BuickGN
. . .
First off, the rod and main bearings are never dry started. I've torn down engines that have sat for years and there's still oil in the bearings.


For Pete's sake, I didn't mean bone dry. As you very well know, bearings are not lubricated by the mere presence of residual oil -- they're lubed by pressurized oil that in essence forces the metallic surfaces apart from one another. If there's a tad of old residual oil in the bearing, and pressure takes a few moments to be established, the only protection the bearing will have in those moments before full pressure is established, will be from the add pack in the residual oil.

Originally Posted By: BuickGN
The only thing I would worry about is the time to the rpm in which it can devolop the hydrodynamic wedge which is viscosity independent. If anything I would think this would be quicker with a slightly thicker coating of oil on the bearings.

I have to respectfully disagree. The "wedge" is not going to form until full (or close to full) oil pressure is established, with the full necessary volume of oil in the bearing space. A small amount of residual oil is better than nothing, but it's no substitute for fresh oil flowing at the appropriate volume and pressure.

Originally Posted By: BuickGN
I was giving you a big "if" when I said miliseconds. We don't know for sure that it takes any longer for a 30wt to reach parts. If the ADBV is working you have oil movement from the first degree of crank rotation.

Two thoughts here. First, right, we don't know. One thing we DO KNOW FOR SURE, is that the 20 wt oils have not been killing engines early by the millions as the early anti-20 Chicken Littles predicted would happen. But common sense would seem to indicate that all things being equal (yes, yes, I know they never are...), the thinner oil is going to get where it's needed faster than a thicker oil.

Originally Posted By: BuickGN
I don't understand this way of thinking. You would rather give up HTHS protection for a thinner viscosity that has never been proven to protect better during startup. I see this "better startup protection" claim go unchallenged too much.

Well, on the flip side, there is no unchallengeable proof that a relatively higher HTHS is more important than the ability to flow quickly on start.

Originally Posted By: BuickGN
My own car has seen excessive wear going from a 50wt to a 30wt. I've seen it with my own eyes, not read about it on an internet forum.


Undoubtedly true, but don't overgeneralize from one data point (which you happen to own...

). Given the other info that's out there, I'd argue that your result is as much a result of the characteristics of your engine, as it is the oils involved. Because this result is not seen in mainstream vehicles driven under typical conditions.

BGN, obviously you and I have somewhat different views on this issue. Please don't mistake that for any lack of respect for your participation here. Have a good and safe weekend.

 

[XS650]

Originally Posted By: ekpolk
For Pete's sake, I didn't mean bone dry. As you very well know, bearings are not lubricated by the mere presence of residual oil -- they're lubed by pressurized oil that in essence forces the metallic surfaces apart from one another.

That's a common misconception. If you look at how the main bearings in a car are lubed, you will see that oil pump pressure actually presses the loaded surfaces together. The pump pressure side is on the bearings unloaded side. The pump and it's pressure is just there to get oil to the bearing. It doesn't contribute directly to the few hundred psi generated by the wedge.

Quote:
If there's a tad of old residual oil in the bearing, and pressure takes a few moments to be established, the only protection the bearing will have in those moments before full pressure is established, will be from the add pack in the residual oil.


The wedge is formed in a fraction of a revolution on residual oil. Car bearings have very delicate surfaces and have been doing fine since well before add packs.

 

[il_signore97]

Originally Posted By: ekpolk
But common sense would seem to indicate that all things being equal (yes, yes, I know they never are...), the thinner oil is going to get where it's needed faster than a thicker oil.



ekpolk, all good points, but I'm just not so sure you can say this. I know it's been said 1000 times, but with a positive displacement pump at idle speed, even with cold oil, I doubt that in a moderate climate that there would be any difference between a 5W20 or a 10W30. The starter will have to put in extra work to get the oil moving, but with every revolution of the pump a (nearly) equal amount of oil comes out. It only has one place to go (the engine), so there's no reason to believe that a 5W20 will lubricate bearings sooner.

Now, in -40 weather, you definitely have a point, as the bypass valve would most likely open up and in that case, thinner definitely equals more flow.

Have a good weekend

 

[BuickGN]

Originally Posted By: ekpolk
Originally Posted By: BuickGN
. . .
First off, the rod and main bearings are never dry started. I've torn down engines that have sat for years and there's still oil in the bearings.


For Pete's sake, I didn't mean bone dry. As you very well know, bearings are not lubricated by the mere presence of residual oil -- they're lubed by pressurized oil that in essence forces the metallic surfaces apart from one another. If there's a tad of old residual oil in the bearing, and pressure takes a few moments to be established, the only protection the bearing will have in those moments before full pressure is established, will be from the add pack in the residual oil.

Originally Posted By: BuickGN
The only thing I would worry about is the time to the rpm in which it can devolop the hydrodynamic wedge which is viscosity independent. If anything I would think this would be quicker with a slightly thicker coating of oil on the bearings.

I have to respectfully disagree. The "wedge" is not going to form until full (or close to full) oil pressure is established, with the full necessary volume of oil in the bearing space. A small amount of residual oil is better than nothing, but it's no substitute for fresh oil flowing at the appropriate volume and pressure.

Originally Posted By: BuickGN
I was giving you a big "if" when I said miliseconds. We don't know for sure that it takes any longer for a 30wt to reach parts. If the ADBV is working you have oil movement from the first degree of crank rotation.

Two thoughts here. First, right, we don't know. One thing we DO KNOW FOR SURE, is that the 20 wt oils have not been killing engines early by the millions as the early anti-20 Chicken Littles predicted would happen. But common sense would seem to indicate that all things being equal (yes, yes, I know they never are...), the thinner oil is going to get where it's needed faster than a thicker oil.

Originally Posted By: BuickGN
I don't understand this way of thinking. You would rather give up HTHS protection for a thinner viscosity that has never been proven to protect better during startup. I see this "better startup protection" claim go unchallenged too much.

Well, on the flip side, there is no unchallengeable proof that a relatively higher HTHS is more important than the ability to flow quickly on start.

Originally Posted By: BuickGN
My own car has seen excessive wear going from a 50wt to a 30wt. I've seen it with my own eyes, not read about it on an internet forum.


Undoubtedly true, but don't overgeneralize from one data point (which you happen to own...

). Given the other info that's out there, I'd argue that your result is as much a result of the characteristics of your engine, as it is the oils involved. Because this result is not seen in mainstream vehicles driven under typical conditions.

BGN, obviously you and I have somewhat different views on this issue. Please don't mistake that for any lack of respect for your participation here. Have a good and safe weekend.

No disrespect taken and none given.

Of course I agree that thinner flows faster in theory but I'm interested when a positive displacement oil pump is thrown in the mix assuming it's not in bypass.

My GN is a bit different. One of my theories I have is I know the crank is flexing and the main caps have shown signs of walking in the past. My car likely requires a very thick oil due to distortion of the bottom end under power and the fact that it makes over 700lbs of torque at the convertor's stall speed of 2,800rpm spread out over only 6 cylinders... Couple that with a narrow bearing small journal crank and there's a lot of psi on the rod bearings.

On the HTHS issue, I'm sure you were around when the thread was posted with GM's testing on the 3.8L with different HTHS values. Wear was something in the order of 1/5 as much with a HTHS in the 3s than a 2.6. I have it saved on my computer at home. I'll post a link if someone doesn't find it first. I don't remember what the conditions of the test were, if it was normal load and rpm or if it was highly stressed.

As for the wedge, I see I was beaten to it already.

As it was mentioned, most rod and main bearings are very fragile. I can scratch them with a fingernail yet they sometimes come out of an engine looking like they have never been touched by anything.

Off topic but I wonder if the amount of VIIs can play a role in the time it takes to form the wedge...

Have a good weekend!

 

[ekpolk]

Originally Posted By: XS650
Originally Posted By: ekpolk
For Pete's sake, I didn't mean bone dry. As you very well know, bearings are not lubricated by the mere presence of residual oil -- they're lubed by pressurized oil that in essence forces the metallic surfaces apart from one another.

That's a common misconception. If you look at how the main bearings in a car are lubed, you will see that oil pump pressure actually presses the loaded surfaces together. The pump pressure side is on the bearings unloaded side. The pump and it's pressure is just there to get oil to the bearing. It doesn't contribute directly to the few hundred psi generated by the wedge.

But how many milliseconds do you suppose that wedge will last without an adequate flow of fresh, pressurized oil to maintain it? Yes, yes, I do understand that the oil pump is a positive displacement device, but it also typically has a relief valve that opens if pressure climbs above a set limit. Consider the hypo of a cold start on a very cold day, with the oil substantially thickened as a result. If the valve opens, how long will the residual oil in the bearing be able to maintain the wedge? Now consider this question: what would you rather count on -- a non-pressurized residual of 30 wt oil in the bearing, or a fully pressurized, proper flow of 20 wt oil?

. . .
Originally Posted By: XS650
The wedge is formed in a fraction of a revolution on residual oil. Car bearings have very delicate surfaces and have been doing fine since well before add packs.
Then why do oil makers bother with EP and AW additives at all? In the days of truly primitive oils, when they did not have sophisticated add packs (or any at all), you would have been lucky for a car to make it to 100k miles. There was a reason for that lack of durability. True, it was not all on the back of the oils, but oil quality (or lack thereof) must have been a important factor.

 

[XS650]

The wedge from residual oil will last seconds, not milliseconds.

The add packs are more for non-hydrodynamically lubed surfaces.

 

[ekpolk]

Originally Posted By: BuickGN
. . .
My GN is a bit different. One of my theories I have is I know the crank is flexing and the main caps have shown signs of walking in the past. My car likely requires a very thick oil due to distortion of the bottom end under power and the fact that it makes over 700lbs of torque at the convertor's stall speed of 2,800rpm spread out over only 6 cylinders... Couple that with a narrow bearing small journal crank and there's a lot of psi on the rod bearings.
. . .
As it was mentioned, most rod and main bearings are very fragile. I can scratch them with a fingernail yet they sometimes come out of an engine looking like they have never been touched by anything.
. . .


I suppose the first statement, quoted above, is one of the best I've seen here for the idea that one oil grade or another is not "better" or "worse" than another. Owners and operators should use that which is optimum for their application. I very, very seriously doubt that I could ever create a situation in which the bearings in my Hybrid Camry's engine ever approach anything like the psi loading your GN's bearings will see. Ergo, I am absolutely unconcerned about the recommendation that states 0w-20 is preferred.

I remember in junior high school shop class, during the automotive part (the only part I really liked, except when my non-friend Paul cut the tip of his finger off in the band saw...

). The teacher had an old Chevy I-6 cut apart as a display, and bearings out for examination. Yes they are soft. But as Mr. Fossil (close to his real name) put it, they got "polished" in use. And they also eventually get worn down. I may be wrong, but I suspect that much of that wearing down happens right after start before OP has been established throughout the oil system.

 

[ekpolk]

Originally Posted By: XS650
The wedge from residual oil will last seconds, not miliseconds.


Perhaps. But I still don't have a "warm fuzzy" feeling about that. I would suspect the actual duration of effective residual protection would depend upon a number of variables that are mostly beyond the operator's control. The two variables that are obviously controllable are: 1) how you treat the vehicle immediately after start, and 2) what oil you choose. As for the latter factor, why not choose the oil that, consistent with what you car otherwise needs, will arrive at critical lubrication points the fastest?

 

[Hitzy]

Originally Posted By: ekpolk
Originally Posted By: XS650
The wedge from residual oil will last seconds, not miliseconds.


Perhaps. But I still don't have a "warm fuzzy" feeling about that. I would suspect the actual duration of effective residual protection would depend upon a number of variables that are mostly beyond the operator's control. The two variables that are obviously controllable are: 1) how you treat the vehicle immediately after start, and 2) what oil you choose. As for the latter factor, why not choose the oil that, consistent with what you car otherwise needs, will arrive at critical lubrication points the fastest?


When looking at cold start up, aren't the differences negligeable between 5w20/5w30 or 0w20/0w30? They are both spec'd to the same cold temp flow range?

 

[ekpolk]

Originally Posted By: Hitzy
Originally Posted By: ekpolk
Originally Posted By: XS650
The wedge from residual oil will last seconds, not miliseconds.


Perhaps. But I still don't have a "warm fuzzy" feeling about that. I would suspect the actual duration of effective residual protection would depend upon a number of variables that are mostly beyond the operator's control. The two variables that are obviously controllable are: 1) how you treat the vehicle immediately after start, and 2) what oil you choose. As for the latter factor, why not choose the oil that, consistent with what you car otherwise needs, will arrive at critical lubrication points the fastest?


When looking at cold start up, aren't the differences negligeable between 5w20/5w30 or 0w20/0w30? They are both spec'd to the same cold temp flow range?


Perhaps. I would assume that the pertinent differences depend upon the engine involved. For some, perhaps no difference. For others, maybe big difference. If there we no important differences between 20 and 30 weights, why bother with the distinction?

 

[BuickGN]

Originally Posted By: ekpolk
Originally Posted By: Hitzy
Originally Posted By: ekpolk
Originally Posted By: XS650
The wedge from residual oil will last seconds, not miliseconds.


Perhaps. But I still don't have a "warm fuzzy" feeling about that. I would suspect the actual duration of effective residual protection would depend upon a number of variables that are mostly beyond the operator's control. The two variables that are obviously controllable are: 1) how you treat the vehicle immediately after start, and 2) what oil you choose. As for the latter factor, why not choose the oil that, consistent with what you car otherwise needs, will arrive at critical lubrication points the fastest?


When looking at cold start up, aren't the differences negligeable between 5w20/5w30 or 0w20/0w30? They are both spec'd to the same cold temp flow range?


Perhaps. I would assume that the pertinent differences depend upon the engine involved. For some, perhaps no difference. For others, maybe big difference. If there we no important differences between 20 and 30 weights, why bother with the distinction?


CAFE..... Sorry, I couldn't help myself.

Personally, I think 90% of the 20wt advantage comes during the warmup cycle in the form of fuel economy. I briefly went to a 0w-20 when I did a job in Lake Tahoe with temps being waaaay below freezing and my typical "commute" being 1.5 miles. This is where these oils shine and I would have no problem running it all the time in one of those climates with short commutes.

But raise the starting temp up 100 degrees to a typical summer day here and the 30wt I have now is still thinner than the 0w-20 at startup in Tahoe. This is why I despise the 20wt for all conditions in some manuals. It makes no logical sense if you're looking at it in terms of the best protection.

 

[XS650]

If you check the charts, the viscosity difference between amid range 20 and a mid range 30 at operating temperatures is about the same as the viscosity change from a 15F temperature change.

But, 20s I have looked at tend to be on the thick end and 30s tend to be on the thin end, so in most cases the difference is less then the equivalent of a 15F temperature difference at operating temperatures.

The fact that 20s tend towards the thick end gives you a hint of what the manufacturers really think about thin oil.

 

[Gary Allan]

There's also considerations of mass marketing of the oil and availability.

Rejecting (putting it aside for the moment) the absolute science/physics that's being cited here, I'd add a couple of things that may alter the view of lower viscosity oils currently gravitating toward the higher end of the scale. I do get the notion that the divisions are arbitrary and the absolute differences aren't all that much.

Bruce can manage a 0w-10 using expensive base stocks since they afford "room" for additives and the required carriers. Any thinner, and volatility climbs to 30%. He'd never be able to do it with a Group II.

I think what I'm saying is: Given that the physics cited is/are immutable, I don't think that they're totally governing. Chemistry, or rather its current limitations, may be just as big if not a bigger player.

You can engineer a more controlled engine environment, but broad enough vi lubricants, without conflicting limitations, have yet to be invented or made marketable.