"Nooks and Crannies" thin oil guys...

[aquariuscsm]

So when you start an engine first thing in the morning,isn`t every part that requires lubrication good and lubed up within miliseconds? Especially since there`s always a film of oil left behind from the previous run of the engine,unless the time it takes for all the nooks,crannies,and small spaces to "pressure up" with oil? I guess I don`t understand the theory that most wear occurs during the first few minutes of operation.

 

[Bryanccfshr]

OK, excepting bypassing a positive displacment pump will pump the same volume of oil. Once the oil reaches a journal bearing for example it is simply supplied to the bearing as a volume flowing over the bearing surface, what is not taken into the bearing overflows out and to the pan. The higher the viscosity the more resistant it is to being pulled into the hydrodynamic wedge of the bearing. This is most apparent at startup. As oils heat up the approach a viscosity that easily is pulled into the bearing. Thinner oils simulates warmer poil at all temperatures and therefore supplies the bearing with volume to fill the wedge more readily.

So Yes the pump pumps the volume and I don't disagree with Buick on that issue, but where is the oil going once it gets to the bearings? Through them or around them?

 

[BuickGN]

Originally Posted By: Bryanccfshr
OK, excepting bypassing a positive displacment pump will pump the same volume of oil. Once the oil reaches a journal bearing for example it is simply supplied to the bearing as a volume flowing over the bearing surface, what is not taken into the bearing overflows out and to the pan. The higher the viscosity the more resistant it is to being pulled into the hydrodynamic wedge of the bearing. This is most apparent at startup. As oils heat up the approach a viscosity that easily is pulled into the bearing. Thinner oils simulates warmer poil at all temperatures and therefore supplies the bearing with volume to fill the wedge more readily.

So Yes the pump pumps the volume and I don't disagree with Buick on that issue, but where is the oil going once it gets to the bearings? Through them or around them?


Well again, why am I not seeing tons of cam bearing wear since it's the tightest bearing clearance in the engine and I run 20w-50 year round?

While I agree that the oil pump is there to pump oil to the bearing, I think that 60-70psi will also help to get it into the bearing.

Think about some main bearings that have the groove in them for oil to be dispersed.. Rods are fed from the crank outward so as the journal spins, oil is being fed around the bearings.

 

[Bryanccfshr]

That's the difference between a hydrodynamic and hydrostatic lubrication circuit(automotive apps are hydrodynamic). Your pump may be pushing high pressure but fluid takes the path of least resistance and is not forced into the bearing, a flow is supplied over the bearing surface what the bearing doews not take flows ovedrfboard down to the pan.

 

[oilyriser]

It would be interesting to know if hydraulically controlled cam phasing systems are switched on only after a certain coolant temperature is reached, assuming that the specified oil was used, and it is of a suitable viscosity at that temperature.

 

[BuickGN]

Originally Posted By: Bryanccfshr
That's the difference between a hydrodynamic and hydrostatic lubrication circuit(automotive apps are hydrodynamic). Your pump may be pushing high pressure but fluid takes the path of least resistance and is not forced into the bearing, a flow is supplied over the bearing surface what the bearing doews not take flows ovedrfboard down to the pan.


The oil is fed from the center out. While some most definately escapes from the sides, I fail to see why this would be worse when the oil is thick.

And if what you say is true and more oil is getting squeezed out of the sides, this would contribute to better cylinder lube, not worse when the oil is cold. Excess doesn't flow down toward the pan, it gets flung around by the crank/rods.

 

[OVERKILL]

Originally Posted By: ekpolk
This is an unfortunate discussion. On one hand, I see the point BGN is making -- there aren't any magical, secret nooks or crannies in an engine. On the other hand, there are some incredibly tight, small clearances in a modern engine. You might very well call the space in a main bearing a "nook" or "cranny". Same for such places as a very, very tight oil passage. The simple fact that is as you get down to the very small passages, the thicker the oil, the harder it will be for it to penetrate in.

Very rarely do I see the "assumption" that 80% or more of wear happens on startup challenged. Yet in a discussion like this, this "axiom" seems to vanish into thin air.

Wear happens on startup because thick cold oil has trouble penetrating into the spaces where it's supposed to do its job. Within the bounds of reason, the thinner the oil you use, the easier it will be for it to get where it's needed quickly.


You must also take into account that the engine's components are not the same size cold as they are hot. You have out-of-round pistons that change shape when they reach operating temperature for example.

It is not as simple as stating that the colder, thicker oil does not lubricate as well, and therefore that is the reason for "more startup wear". There are a number of contributing factors.

Diesel engines run tighter clearances than gasoline engines, yet spec heavier oils..... Something to consider when contemplating your main bearing argument.

 

[Sayjac]

Originally Posted By: MarkC
In my case, it doesn't serve much purpose for me to ponder too long the virtues of thick vs. thin. If I want to give Chrysler (or whatever it becomes) no reason to void the lifetime warranty on my new Jeep, I'll be using 5W20, like it says in the manual, the service manual, and on the oil filler cap. Unless I change my mind.

Geez, manual, service manual, and oil filler cap, no kidding? What a novel idea, following what those say so as not to void your warranty. Just like Honda, with no mention in the manuals, of using a heavier oil (I checked). Now that sounds like 'common sense' to me.

Forget the fact that 5w20 oils are very well engineered oils.

 

[Hitzy]

Which oil weight gives better protection at higher heat?
20w or 30w?

 

[StevieC]

Originally Posted By: Hitzy
Which oil weight gives better protection at higher heat?
20w or 30w?
Depends on the engine design, the oil used, and the driving condition... Not a simple answer IMO!

 

[ekpolk]

Originally Posted By: Hitzy
Which oil weight gives better protection at higher heat?
20w or 30w?


This simple looking question reveals one of the key flaws in this whole "debate". My answer would be, "it depends...," or "need more information...". You simply can not make generalizations about one oil grade or another without, in this case doing some of the following: 1) define "better", 2) specify the engine involved, 3) specify how the engine will be used, 4) define "higher heat", -- are you talking about the upper end of the engine's operating range, or an overheat, and so forth. I'm sure the engineers (mechanical and chemical) can come up with more.

Finally, you didn't really mean 20w and 30w, did you? I assume we're talking about the xw-20 or xw-30 oils.

 

[Hitzy]

Originally Posted By: ekpolk
Originally Posted By: Hitzy
Which oil weight gives better protection at higher heat?
20w or 30w?


This simple looking question reveals one of the key flaws in this whole "debate". My answer would be, "it depends...," or "need more information...". You simply can not make generalizations about one oil grade or another without, in this case doing some of the following: 1) define "better", 2) specify the engine involved, 3) specify how the engine will be used, 4) define "higher heat", -- are you talking about the upper end of the engine's operating range, or an overheat, and so forth. I'm sure the engineers (mechanical and chemical) can come up with more.

Finally, you didn't really mean 20w and 30w, did you? I assume we're talking about the xw-20 or xw-30 oils.


Yes....xW-20 & xW-30. I know they are both suitable for temp an engine will reach under normal operating conditions, I'm not trying to make this a complicated question, just asking which has the ability to protect to a higher temp.
If you want an example, how about if you get a stone through your rad and for some reason can't pull over right away and your engine overheats. Which oil would protect better in an overheated engine situation?

 

[BuickGN]

Originally Posted By: Hitzy
Originally Posted By: ekpolk
Originally Posted By: Hitzy
Which oil weight gives better protection at higher heat?
20w or 30w?


This simple looking question reveals one of the key flaws in this whole "debate". My answer would be, "it depends...," or "need more information...". You simply can not make generalizations about one oil grade or another without, in this case doing some of the following: 1) define "better", 2) specify the engine involved, 3) specify how the engine will be used, 4) define "higher heat", -- are you talking about the upper end of the engine's operating range, or an overheat, and so forth. I'm sure the engineers (mechanical and chemical) can come up with more.

Finally, you didn't really mean 20w and 30w, did you? I assume we're talking about the xw-20 or xw-30 oils.


Yes....xW-20 & xW-30. I know they are both suitable for temp an engine will reach under normal operating conditions, I'm not trying to make this a complicated question, just asking which has the ability to protect to a higher temp.
If you want an example, how about if you get a stone through your rad and for some reason can't pull over right away and your engine overheats. Which oil would protect better in an overheated engine situation?


What it may come down to is HTHS. It's been proven though some still debate it that a higher HTHS will protect better under high heat and stress. Most 30wts will have a higher HTHS than most 20wts. To all you thin guys, notice I said "most". No need to bring up Redline.

 

[440Magnum]

Originally Posted By: aquariuscsm
Something I`ve always wondered,are newer engines machined with more precision,making thinner oils more compatible per se?


The specified clearances in reciprocating engines haven't really changed a lot in 40 years. Hypereutectic pistons are *cold* fitted much tighter than forged or autothermic cast pistons, but at operating temperature the clearances are the same. Bearing clearances are about the same, too.

What's changed most is the reduction/elimination of high-pressure sliding contact points, like gear drives and flat-tappet cams. Most newer car engines don't even have a gear-driven oil pump anymore, its driven directly off the crank.

Also there are now mechanisms (MDS, VVT, etc.) in some engines that *require* thinner oil to operate correctly.

Actually, let me re-state that. I don't believe that they necessarily REQUIRE thinner oil to actuate correctly, but the computer systems that control them have to be programmed with an assumption about how thick the oil is based on temperature- because that's all the computer can measure- engine TEMPERATURE. So the system is correctly calibrated for the (usually thin) oil that the factory specifies, and may not actuate at quite the same speed or delay as the computer programming expects if you substitute a 50-wt oil and the computer calibration assumes 20-wt oil.

 

[ekpolk]

Originally Posted By: Hitzy
...
Yes....xW-20 & xW-30. I know they are both suitable for temp an engine will reach under normal operating conditions, I'm not trying to make this a complicated question, just asking which has the ability to protect to a higher temp.
If you want an example, how about if you get a stone through your rad and for some reason can't pull over right away and your engine overheats. Which oil would protect better in an overheated engine situation?


It probably still depends upon which type of oil (as distinct from vis grade) and what sort of engine has the problem. For example, I suspect that Redline 0w-20 would probably stand up to an overheating better than a thick G-II 5w-30. As for engine design, probably depends upon how tolerant a given engine is for its oil thinning with heat. If the design is intolerant of thinned oil, perhaps the 30 wt provides an extra margin over the 20 wt. If the engine "doesn't care" then no added advantage. In short, it's not about a given oil's grade and makeup looked at in isolation, it's how the whole thing works together. IMO.
==============================================================

Originally Posted By: BuickGN
...
What it may come down to is HTHS. It's been proven though some still debate it that a higher HTHS will protect better under high heat and stress. Most 30wts will have a higher HTHS than most 20wts. To all you thin guys, notice I said "most". No need to bring up Redline.


I already mentioned Redline.

I too keep an eye on the HTHS values. Personally, I suspect that on this dimension, engines fall roughly into two categories -- those that respond to different HTHS values, and those that don't (within the bounds of reason, I suppose you could make any engine respond by going to extremes). For the former category, owners might see a difference; for the latter, they won't.

At the end of the day, however, even if one concludes that on some level 30 wt oils generally protect better than 20 wt oils (whatever "better" means), it must be on a level of virtual insignificance. Again, over eight years since the xw-20 oils became widely specified by car makers, and we're still not seeing any indications of automotive engine destruction as a result. I suppose the counter-question for all you thick oil devotees is this: where are all the junkyards full of dead Fords and Hondas that were killed by their thin oil???

 

[ekpolk]

Originally Posted By: 440Magnum
...
What's changed most is the reduction/elimination of high-pressure sliding contact points, like gear drives and flat-tappet cams. Most newer car engines don't even have a gear-driven oil pump anymore, its driven directly off the crank.

An interesting observation in this context. One might be tempted to conclude that this reduction/elimination would weigh in favor of lighter oils. But in reality, wouldn't the additive package (EP and AW especially) be more critical in protecting at these locations than the base oil itself?

Originally Posted By: 440Magnum
Also there are now mechanisms (MDS, VVT, etc.) in some engines that *require* thinner oil to operate correctly.

Very true. Another good reason not to deviate far from the "official" (I hate that word...) recommendations.

 

[440Magnum]

Originally Posted By: ekpolk
Originally Posted By: 440Magnum
...
What's changed most is the reduction/elimination of high-pressure sliding contact points, like gear drives and flat-tappet cams. Most newer car engines don't even have a gear-driven oil pump anymore, its driven directly off the crank.

An interesting observation in this context. One might be tempted to conclude that this reduction/elimination would weigh in favor of lighter oils. But in reality, wouldn't the additive package (EP and AW especially) be more critical in protecting at these locations than the base oil itself?


That would be my ASSumption. Earlier in the thread I flat-out stated that for the most part I don't think viscosity matters a great deal- the difference between how fast 20wt and 50wt will get "squeezed" out of a rod bearing when the cylinder attached to the rod fires is pretty trivial. Viscosity DOES matter if there's enough pressure loss that you don't get even oil distribution with thin oil. I'm sure it also doesmatter at least somewhat in how long the hydrodynamic regime lasts vs. transition to the regime where you need EP/AW... but I think a lot of people overestimate its effect there.

Originally Posted By: ekpolk
Originally Posted By: 440Magnum
Also there are now mechanisms (MDS, VVT, etc.) in some engines that *require* thinner oil to operate correctly.

Very true. Another good reason not to deviate far from the "official" (I hate that word...) recommendations.


I may have edited after you quoted this, but I did put in a comment that I believe the engine management systems are calibrated to activate the VVT and MDS systems in accordance with a particular thickness/temperature profile. I have no doubt that the systems could be made to work perfectly with 50-wt oil too. The manufacturers choose not to.

 

[ekpolk]

Originally Posted By: 440Magnum
...
I may have edited after you quoted this, but I did put in a comment that I believe the engine management systems are calibrated to activate the VVT and MDS systems in accordance with a particular thickness/temperature profile. I have no doubt that the systems could be made to work perfectly with 50-wt oil too. The manufacturers choose not to.



But remember, every company that sells cars in the US sells them in all 50 states (yes, I know, there are complexities I'm ignoring here...). With that in mind, the car makers have to be sure that what they sell will work in Alaska or Minnesota in February just as well as it works in Miami in August. A tall order for sure, but I suspect the only way to meet that would be with a "thin" oil -- like a 20 wt.

Remember too, that irrespective of vis grade, as long as it's a liquid, it's a non-compressible fluid (compressible fluids, of course, being the gasses). As much difference as there may be between a cold SAE 60 oil and a hot 20wt, they're both non-compressible fluids, and thus "eligible" to perform as hydraulic fluids for things like MDS and VVT-i.

 

[Audi Junkie]

Originally Posted By: Hitzy
Which oil weight gives better protection at higher heat?
20w or 30w?



What makes you think you have "high heat"?

 

[simple_gifts]

Originally Posted By: javacontour
Originally Posted By: simple_gifts
They hold the melted butter.


Isn't that the Thomas English Muffins line?


That is correct.