0W-40 pros & cons...

[demarpaint]

Originally Posted By: Trav
Some of the newer engines are specifically designed for xw20 oil verses engines that were designed for multiple grades that can use xw20 and get by with it.
If the engine is designed for it there is no benefit in going with heavier weight oil, in fact with the clearances and surface finish on the crank and dual stage oil pumps it may be detrimental.


Great point, operative words being "designed for it." There are a lot of cars on the road, that were spec'd for 20 grade oils and in earlier applications calling for 30 grade oils. They still have the same internal engine design, using the same crankshaft, bearings, cam, lifters, etc. as older model years with the same engine did. The only difference being the model year and oil spec, not a change in design. Clearly CAFE generated. Having said all of that your statement is correct, if the engine was "designed" specifically to run a 20 grade oil there is no benefit in bumping a grade, and in doing so it may very well damage the engine.

 

[Shannow]

Trav,
wasn't ignoring part 2 and 3, was just at a place where I don't have my normal supply of stuff...spend nearly 10 hours a day there, 5 days a week...

Originally Posted By: Trav
What about multi stage/variable oil pumps like the pendulum-slider that are becoming more common that can maintain pressure and flow of the thinner oils at operating temp?


Here's a typical crank mounted pump, old style, and the new version of variable displacement pump.



Old style pumps the same volume of oil every revolution, and has to provide enough oil for low RPM operation. So at high RPM, it pumps WAY too much. The engine won't take that volume (oil pressure will go through the roof), so a relief valve is installed to divert the excess oil back to the sump (or worse the pump suction)...this needlessly heats the oil, and wastes power (about as much as a headlight or two, but it's waste, 24/7).

The new style gives the same volume at low revs, as it's needed, but the hinged inner pump body and spring replaces the relief.

As the pressure rises, the inner body compresses the spring, and the relationship between the vanes and the housing changes, reducing the delivery volume. Pressure is the signal that the engine doesn't need any more oil.

The pumps aren't "optimised" to deliver the correct volume and pressure, but are optimised to not over deliver like a traditional set-up.

All up, it saves 50-150W...that's worth it.

 

[Shannow]

Originally Posted By: Trav
Given the optimal pressure and volume these pumps provide is the film strength of the thinner oil similar when bearing clearances are reduced?


OK, a couple of parts to this part.

Some guy Sommerfeld did a load of work on bearing design back in the day, and has a dimensionless number named after him, the Sommerfeld number, which can be used for design and scaling...

So = (r/c)^2 x u x N / P

r is the shaft radius
c is the clearance
u is Kinematic Viscosity
N is shaft speed
P is bearing load (load/(2xrxl)) where l is the bearing length.

And from this, there are a bunch of curves...first I'll do is Minimum Oil Film Thickness (MOFT).



the max W line is the max power loss line. the min F line is the minimum friction line.

Use the line of L/D = 1/4 as an example, as that's close to the L/D of an engine bearing.

mentally mess with the parameters.
* Increase speed - MOFT goes up
* reduce P (say make the bearing longer a tad) - MOFT goes up.
* increase r - MOFT goes up
* reduce c - MOFT goes up.

And you have stated, correctly many, many times in the past that blocks with their deeper skirts and cross bolting are SOOOO much stiffer in the bottom end, that clearances can be reduced to avoid contact...it's all part of the equation.

 

[Shannow]

Next part is flow...flow doesn't lubricate, nor does pressure.

Pressure supplies oil to the bearing, and the bearing characteristics determine how much flow passes through it.

Same So number as before, but this is the chart of how much oil leaks out the side of the bearings, and has to be replaced by the oil pump.


Again, look at the l/d=1/4 line.

Move the So number to the Right, and the oil requirement reduces.

So with regard to the oil pump design, at low speeds (low N), you need more oil per revolution than at higher RPM.

Old pumps overdeliver at high RPM, and waste it through relief, new pumps back off delivery volume to match requirements.

Nice little summary in this table...

 

[Shannow]

Originally Posted By: PimTac
And this is another episode of The Thick and Thin Oil Turns, the most popular soap opera on BITOG.


and note to all, the last couple of posts aren't thick/thin, as they've been accused of often in the past (not saying you).

It's simply how the world works, and I am explaining how the world works so that people better understand the relationsships.

The OTR truck engine manufacturers are trying a different tack in that some trials are thermal barrier cotings on the water side of the cylinder liners mid stroke, so that the local oil film is quite a lot hotter (and thinner) than the viscosity at TDC and BDC...they are trying to reduce the power sapping effects of shear in the high velocity mid stroke area, while keeping the viscosities elsewhere up.

There's a LOT available in an car engine...



Like I said re Honda, they are appearing to chase the piston friction at present with lower Vis...and beefing up the bearings, costing power, but pushing them to the right of the So/MOFT line.

 

[Shannow]

As to 0W40 pros and cons...

IMO, it's nearly the universal oil...anywhere on the globe, you could run anything on it either completely or reasonably successfully (D11s dozers, and 2 stroke diesels would probably be the marginal end of it, automobiles the completely successful end).

Try the above with a 0W20, and you will quickly find a different outcome.

(Oz, an SAE30 would get you anything that NEEDS doing).

 

[SR5]

Thanks Shannow. Very helpful.

 

[kschachn]

Originally Posted By: oil_film_movies
Originally Posted By: kschachn
So how many of those actually sheared out of grade? Two? Did any make it down to a 20 grade like you postulated?

All did.
Do you know 12.5 cSt kv100 is a 40?
Want me to find more? Why don't you? Like all the question marks? Isn't that the way all your posts are????
As I said, add in DI or DI-turbos like Ecoboost or Honda Turbos like we've seen lately, and you'll be in the 20 weight area quickly with possible fuel dilution. Read my post again. Stop picking the 20 weight mentioned and concentrate more on the 30 weight stuff, as thats more likely between the two over a fleet.
Can you look up your own answers?

Thanks for the response despite the underlying anger. Why is that?

I picked the 20-weight because you said that, no other reason.

And yes I can look up my own answers. I only asked because of your statement.

 

[NGRhodes]

Originally Posted By: Shannow
Originally Posted By: PimTac
And this is another episode of The Thick and Thin Oil Turns, the most popular soap opera on BITOG.


and note to all, the last couple of posts aren't thick/thin, as they've been accused of often in the past (not saying you).

It's simply how the world works, and I am explaining how the world works so that people better understand the relationsships.

The OTR truck engine manufacturers are trying a different tack in that some trials are thermal barrier cotings on the water side of the cylinder liners mid stroke, so that the local oil film is quite a lot hotter (and thinner) than the viscosity at TDC and BDC...they are trying to reduce the power sapping effects of shear in the high velocity mid stroke area, while keeping the viscosities elsewhere up.

There's a LOT available in an car engine...



Like I said re Honda, they are appearing to chase the piston friction at present with lower Vis...and beefing up the bearings, costing power, but pushing them to the right of the So/MOFT line.


Which paper is that table from (I have academic access) ?

 

[aquariuscsm]

So in layman's terms,my Accord only gives me 0W20 as an option,no climate table like in my Nissan. Does that mean Honda designed this version of the K24 around a 0W20 oil? The earlier versions of the K24 that are specd other weights than 0W20 have a different model code/number

Haha yes,all the uber tech stuff goes WAY over my head

 

[Virtus_Probi]

Originally Posted By: Shannow
Originally Posted By: PimTac
I still want to hear a plausible explanation how reducing the amount of oil in the sump will reduce drag. That CRV of dblshock has a very small capacity sump anyway. 3.5 qts?? So how much? 1/2 qt? 1qt?


splash lubricated it would, but you don't see that much these days.

In gearboxes and diffs, running them low reduces parasitic drag (by a little)


Could it be argued that a splash lubricated system with a low sump would give you less protection than one with a full sump?

Thanks for posting all the detailed charts, BTW...even as an engineer (electronics) who loves looking at plots, I don't know that I'll ever really digest much of the info you present here. But, I do feel like I get something from it...the summaries showing nearly identical flow for 0W20 and 20W50 in the same conditions definitely stuck with me.

 

[Bxnanaz]

Originally Posted By: Panzerman
Most people are going to use whatever that manual says.
They will never step back and look at it or have any real world experience with such things. The rest will think outside the box and realize light oil/ cafe standards and smaller passages with tighter clearances are total nonsense.


Existing engines that were spec’d for 30 and now are spec’d for 20, sure. I wouldn’t doubt an engine like the gen v GM 5.3 was built with 0W20 in mind.

 

[Trav]

Originally Posted By: Shannow
Originally Posted By: Trav

Shannow, you may be able to answer the questions that come to mind.

If the bearing clearances are smaller cold do they not get even smaller at operating temp?


Trav,
take a 1.995" steel bar in a 2.000" steel hole, and heat them, the clearances will stay the same at 0.005".
take a 1.995" steel bar in a 2.000" aluminium hole and heat them, and the clearances open up.

The heat in the bearings that the oil "carries away" is the heat generated in the bearing, and it flows from the oil film INTO the block and INTO the crank, meaning that at operating temperature, the temperatures in both components are about the same.



Iron crank/iron block, no change in clearance.
Iron crank alloy block, they open up.


Thanks for that Shannow.

 

[wemay]

 

[wemay]

 

[claluja]

Thanks for posting article. So seems like Mg and Mo aren't real good together, and that alot of the new oils coming out are increasing Mg (and reducing Mo) in order to deal with LSPI in direct injection engines.

This begs the question for a guy like me with no direct inject engines, wouldn't I be better off with less Mg and more Mo.

 

[AZjeff]

Originally Posted By: claluja

This begs the question for a guy like me with no direct inject engines, wouldn't I be better off with less Mg and more Mo.


And part B of the above question, what about GDI but no turbo? LSPI doesn't seem to be a problem when the engine is N/A.

thanks

 

[wemay]

^ This is true, but the OP Civic is a 1.5L Turbo.

 

[Ifixyawata]

I really really like the idea of a 0w-40 and have seen lots of folks on here agree with the 'universal oil' statement. I wish I could find some at AZ clearance some year... I would buy it with reckless abandon. (Oh wait, I do that no matter what the weight is.)

 

[kschachn]

Originally Posted By: Ifixyawata
I really really like the idea of a 0w-40 and have seen lots of folks on here agree with the 'universal oil' statement. I wish I could find some at AZ clearance some year... I would buy it with reckless abandon. (Oh wait, I do that no matter what the weight is.)

That's probably not going to happen, but buying it at Walmart with the rebate will come pretty close to a "clearance" price.