Rod and Main bearing clearance

[Bryanccfshr]

Originally Posted by StevieC
Not looking for an argument, but the nonsense here drives me crazy. Especially when real world evidence contradicts it. Enjoy your day as well.


The evidence is that most modern engines are tolerant to a wide range of viscosities.
Merry Christmas! I Worry more about direct injection soot, air filtration and my tire inflation than if the 0w20 or 0w40 which I run at different times in the same vehicles, is harmful or wonderful.

 

[StevieC]

I'm not saying it isn't tolerant to a range of viscosities, it would have to be when the engine is cold and the viscosity is much thicker than at operating temperature. This would cause excessive engine wear if it weren't. What I'm talking about is the culture here of keeping it thicker than the engineers call for because that somehow offers better longevity when there is no real world evidence, even well past the junk points of most vehicles. And there is proof here from users to prove that.

There are many things that can affect what's good for one vehicle versus another which is another reason blanketing "Thicker is better" is even more ridiculous.

I'm out now, gotta go up to my folks house for dinner.

 

[tig1]

Originally Posted by OVERKILL
Also, FWIW, the BMW S62 (which spec'd 10w-60) apparently had rod bearing clearances of 0.029mm to 0.067mm; 0.0011 to 0.0026 thou, VERY similar to the Duratec.

However the BMW has more than double the clearance that my Fords have. OOPS! My bad. I'm comparing main to Rod.

 

[OVERKILL]

Originally Posted by StevieC
My point is we shouldn't be playing engineer here.


One of the posters who you've had the most issue with, Shannow, is a Mechanical Engineer who specializes in bearing design.

Originally Posted by StevieC
If the engineer calls for a 20wt, use a 20wt. If they call for a 30wt use a 30wt. But blanket statements here of using 30 or 40 weights in applications that call for 20wts because it will somehow offer better protection because of international manuals allowing for 30wts to be used is just ridiculous.


Engineers don't write owners manuals, can you imagine the disaster they would be if they did?

However, if Engineering input was freely allowed into what you received you would still see a range of viscosities recommending what's ideal for the anticipated operating conditions, which we used to see, and is still seen in some instances abroad. Due to CAFE, this is not possible, the oil that the CAFE qualification was run on must be the spec lubricant IIRC.

Subsequently, we've witnessed the introduction of thermal castration mechanisms that limit specific output if oil temperature gets too high. We've seen more widely the use of heat exchangers to control oil temperature and we've seen the mechanical design changes I've noted to the engines themselves to ensure that they'll survive properly on thinner lubricants.

None of that means that an engine is going to die prematurely on 0w-20 or 5w-20. It may mean slightly better wear performance if one were to do a tear down while running an xW-30 or xW-40, but that may be of zero consequence over the useful life of the equipment. We've had this discussion before. The other side of "better than" is not a pile of failed engines. We are talking what is likely a marginal improvement over what is already acceptable. It has to be acceptable, because it's what is spec'd for the expected lifetime of the equipment. And these improvements are likely only in certain areas.

Also, there is the drive for and expectation of universal lubricants which is why 0w-40 has become so popular for performance applications. The aforementioned lubricant chart can be greatly decreased in complexity due to the availability of these broad spread oils. Ergo, the Corvette has spec'd 5w-30 and 15w-50 and now 0w-40, Ford got away with just spec'ing 5w-50 but could have done a 5w-20/5w-50 recommendation. FCA went with 0w-40. The 5.7L HEMI has also simultaneously spec'd 5w-20 and 5w-30 depending on application. Without CAFE the former would have perhaps spec'd both.

We still see some of this verbiage hinted at in some manuals where there is a remark that a heavier lubricant may be preferable when towing for example or something similar. But it's not a requirement; it can't be for an application for which CAFE credits are claimed. Without that requirement you'd likely see less ambiguous language.

 

[OVERKILL]

Originally Posted by tig1
Originally Posted by OVERKILL
Also, FWIW, the BMW S62 (which spec'd 10w-60) apparently had rod bearing clearances of 0.029mm to 0.067mm; 0.0011 to 0.0026 thou, VERY similar to the Duratec.

However the BMW has more than double the clearance that my Fords have. OOPS! My bad. I'm comparing main to Rod.


No worries. I hope that some of this discussion has been of some value to you. You did bring up a neat example with that 4.0L, which seems to be the real exception here, rather than your Duratec, which appears to be more typical based on the other examples we've looked at.

 

[69Torino]

The oil viscosity should be matched moreso to the operating conditions and usage patterns than to what you think your rod and main bearing clearances are. When I build an engine, loose or tight, I spec the oil viscosity based on the intended usage of the engine. Very rarely do I ever find the need for over a 30 weight oil. The only two times I ran a 50 is on my nitrous Mustang and my nitrous Thunderbird. Before the kits went in them I ran them on 30, and the small block I tore down from the mustang was in serviceable condition. I tore it down because I melted the ring lands off with a lean 175 shot, not because of reciprocating assembly problems.

I have two cars in my driveway with half a million miles combined, and they have spent most of their life on 20 weight. I had the Santa Fe on 30 for a while, but it's now back on 5w-20 Mobil 1 AP because I got it super cheap. When the 20 is used up, back to 30 weight Maxlife Synthetic it goes. Honestly there is zero difference between the two performance-wise, only the price paid.

I'm positive the Hyundai and the Freestyle will crumble around the drivetrain no matter if there is 5w-20 or 5w-30 in the pan.

To summarize, base your decision of viscosity on usage patterns and engine load. Not what's printed on the oil cap. There are differing reasons to use different viscosity oils, whether it's a grocery getter, hot rod, race car, boat, truck, tractor or whatever.

 

[ZeeOSix]

Originally Posted by tig1
Seems to be a good argument for 20 wt oils.

More viscous oil even in tight clearances bearings will give more MOFT, which means more protection from metal-to-metal contact and therefore less bearing wear.

As the graph shows, running thin oil in large bearing clearances can be bad. But it's not bad in terms of MOFT to run thicker oil in tighter clearances.

Another thing to consider is that tighter clearances will heat up the oil more as it's getting squeezed and sheared. So even xW-20 heats up to a certain degree in tight bearings, and depending on the temperature rise, can cause the viscosity inside the bearing to decrease and result in decreased MOFT. That's part of the equation on what determines the MOFT when looking at bearing clearance vs viscosity.

 

[ZeeOSix]

Originally Posted by StevieC
My point is we shouldn't be playing engineer here. If the engineer CAFE calls for a 20wt, use a 20wt.


Fixed it for ya. All the engineering information (those scary SAE papers and graphs) says that thicker oil gives more MOFT which protects bearings better. Higher viscosity oil also typically means better HTHS which is part of the protection factor.

 

[spasm3]

I posted this back in sept.

"An 8th generation honda accord main bearing clearance is .0007 to .0016 inch. A b18 engine which was spec'd for 5w 30 oil , main bearing clearance is ( guess what!!!) .0007-.0016"

Is tig 1 comparing engines with similar cranks? The clearances will be different for different journal sizes.

A 98 honda f23 calls for 5w 30 and a 2001 honda f23 calls for 5w20. Yet both engines use the same main bearing set. ( sealed power 7102m).

 

[fdcg27]

Agree completely.
How an engine is used and how hard it can be made to run means everything WRT oil grade selection, particularly HTHS.
As most of use most of our cars most of the time and given just how hard most of our cars can be run even if we drive hard, thinner grades are more than adequate.
A relatively impotent engine driven in typical North American conditions will be quite fine on a thin grade oil. Take that puppy to the track and something thicker might well be appropriate.
Many of us here have experimented with various grades. The differences you can actually feel and measure in typical use are very small, so those who want to use a thicker grade should have at it without any undo concerns about fuel economy.
They will be giving up a real if small increment in fuel economy while not extending the life of their vehicle as a whole at all.
The yard won't pay you more for an EOL beater just because you fed it M1 0W-40 rather than 0W-20 AFE throughout its working life.

 

[BrocLuno]

Originally Posted by PeterPolyol
Most aluminum blocks will have iron journal bearing carriers


Originally Posted by OVERKILL


You'll note that the mains are quite similar with rod bearings being even tighter. Desired clearance depends on diameter and width, if it was as simple as your posit, the 302 would be an ideal candidate for 0w-8. As with many things, this is a far more complex topic than it is often presented.

It might be a candidate for thin oils, except for the other lacking things..... surface finishing (microfinishing, induction hardened from the factory on a 302? lol), forged steel vs cast iron, metallurgy (iron alloy), and most likely a sub-par oiling system by today's standard. If a 302 has all that, plus minimal manufacturing part varience and a top notch oiling system like a newer engine series, why not then. Not that a 302 is a tighter or looser engine than the Duratec, it's just got a wider (see: sloppier) tolerance. There's not a chance 302 were realistically being pumped out with the narrow, consistent variations than engines leaving the assy line now days are


+1

 

[ChrisD46]

In my Hyundai 2.4L GDI engine the oil cap states 5W20 while the manual states 5W30 and 10W30 are acceptable (depending on ambient temps , towing , etc.) ... Assuming Hyundai also has similar bearing clearances - what would you make of the Hyundai stated oil weight ranges ?

 

[Shannow]

Originally Posted by StevieC

This is going to break BITOG.

No, the Amsoil advertorial was painting a picture that was not technically correct, and you (again) defended it to the death as science...

The clearances haven't changed that much, as many of us keep saying...

There's no need for "thinner" oils to get into those "narrow" spaces...they've always been just as narrow since engines had full pump supplied lubrication systems.

Here's the specs for a 1968 Chev engine as sold in Holdens in Australia....

 

[Shannow]

Originally Posted by tig1
I checked out the main, rod, and piston to pin clearance for the Ford Fusion 2.3 and 2.5 engines I now own.

Main: .0007 to .0013 = 6 10 thousandths of an inch.

Rod bearing clearance: .001 to .002 = 1 thousandths of an inch

Piston to wrist pin clearance: .0003 t0 .0006. 3 10 thousandths of an inch.

I also checked the main clearance in a 30 year old Ford 4.0 ( aprox age) and the clearance was about 3 times the clearance of my Ford engines I own now. Something like .0005 to .0022. That's .0017 10 thousandths of an inch. Seems to be a good argument for 20 wt oils.

I would guess these clearances are the same for the Mazda engines as well.


I'm not sure on the veracity of your argument tig1.

What does subtracting the min clearance from the max clearance tell you (in engineering terms) that validates thinner oils ?

Bear in mind, as an engineer, who has designed bearings for steam turbines (and other things) that sit there and spin 8,760 hours per year on a film of ISO32, I've NEVER used the difference in max to min design clearance for anything design related.

You check the MOFT, oil side leakage, and temperature rise at either end of the clearance range, and design for the middle...the min and max allowable aren't the design point, they are how far away from the design point will give you acceptable operation.

 

[Shannow]

Some more data for the discussion...
3 generations of Holden 6 (1974, 1978, and 1985)
J car as it was sold in Australia in mid '80s)
Nissan Pulsar as sold in Oz in the late '80s, (Had the Holden/Opel J Car engine in it).

 

[beanoil]

Originally Posted by OVERKILL
Originally Posted by StevieC
I think we need to trust the engineers that made the vehicle and this is proven by the longer OCI's that tig1 does and with low viscosity oils. His engines haven't shown any reason not to decrease the OCI or increase the oil weight and has decent miles to prove it along with others here.

I think this is more trust worthy than what folks on an oil forum think is best. Heck we even have really high mileage engines on here run on these 20wt's and they have all survived just fine well past tig1's mileages.

I think it's overblown outside of certain applications that need it. Towing/Turbo's/racing and the like.

But that's not what the topic of the OP was, nor your snipe at the direction your Amsoil thread went, where this topic was discussed in detail. I even posted the exact same clearance numbers for the 302 in that very thread. You obviously didn't come away from that discussion with more knowledge about the topic than when you made it, otherwise your initial post in this thread would have been one of education rather than sour grapes.

Bearing clearances haven't changed significantly. We had boats that spec'd 20W back in the day for cold weather operation and many tractor manuals recommended thinning your oil with kerosene in colder months. Engines are generally quite tolerant as to viscosity selection which is why many engines were safely back-spec'd to 5w-20 when it became widely available. Architectural changes such as block rigidity (deep skirting, multi-bolt mains) has been where the effort was placed, since things moving around has a negative impact on component life, particularly when viscosity is reduced.

Does Ford have a generally solid track record of performance in applications spec'ing xW-20 lubricants in the past two decades or so? Yes. Have bearing clearances changed to accommodate that? No. That's why the Coyote was able to simultaneously spec 5w-20 and 5w-50 depending on the trim level of your Mustang GT, which I also posted in your thread. Have there been structure changes to these engines to facilitate this success? Yes. Both the HEMI (which simultaneously spec's 5w-20 and 0w-40) and the Modular family have deep-skirted blocks with multi-bolt mains designed to provide an extremely rigid structure to house the crankshaft.

So no, the argument that the bearing clearances presented in the OP doesn't make a case for 20-weight oils, just as remarking on the rod bearing clearances for the 302 doesn't make a case for 0w-8.

His track record of performance using the lubricant spec'd by the manufacturer validates Ford/Mazda's designs and testing that resulted in them determining that xW-20 was an appropriate lubricant for these engines under the intended and expected operating conditions, not the fact that the rod bearing clearances are tighter than the Cologne 4.0L V6 or looser than the ancient Windsor, it's a red herring.


2018 winner of 'Most Accurate and Well Explained" post.

 

[JLTD]

Originally Posted by OVERKILL


Engineers don't write owners manuals, can you imagine the disaster they would be if they did?

However, if Engineering input was freely allowed into what you received you would still see a range of viscosities recommending what's ideal for the anticipated operating conditions, which we used to see, and is still seen in some instances abroad. Due to CAFE, this is not possible, the oil that the CAFE qualification was run on must be the spec lubricant IIRC.

Subsequently, we've witnessed the introduction of thermal castration mechanisms that limit specific output if oil temperature gets too high. We've seen more widely the use of heat exchangers to control oil temperature and we've seen the mechanical design changes I've noted to the engines themselves to ensure that they'll survive properly on thinner lubricants.

None of that means that an engine is going to die prematurely on 0w-20 or 5w-20. It may mean slightly better wear performance if one were to do a tear down while running an xW-30 or xW-40, but that may be of zero consequence over the useful life of the equipment. We've had this discussion before. The other side of "better than" is not a pile of failed engines. We are talking what is likely a marginal improvement over what is already acceptable. It has to be acceptable, because it's what is spec'd for the expected lifetime of the equipment. And these improvements are likely only in certain areas.

Also, there is the drive for and expectation of universal lubricants which is why 0w-40 has become so popular for performance applications. The aforementioned lubricant chart can be greatly decreased in complexity due to the availability of these broad spread oils. Ergo, the Corvette has spec'd 5w-30 and 15w-50 and now 0w-40, Ford got away with just spec'ing 5w-50 but could have done a 5w-20/5w-50 recommendation. FCA went with 0w-40. The 5.7L HEMI has also simultaneously spec'd 5w-20 and 5w-30 depending on application. Without CAFE the former would have perhaps spec'd both.

We still see some of this verbiage hinted at in some manuals where there is a remark that a heavier lubricant may be preferable when towing for example or something similar. But it's not a requirement; it can't be for an application for which CAFE credits are claimed. Without that requirement you'd likely see less ambiguous language.


Overkill, thanks for summing up all the arguments about CAFE and thick vs thin in once concise and intelligent post! You've said here what I've been trying to say for some time....

 

[demarpaint]

Originally Posted by JLTD
Originally Posted by OVERKILL


Engineers don't write owners manuals, can you imagine the disaster they would be if they did?

However, if Engineering input was freely allowed into what you received you would still see a range of viscosities recommending what's ideal for the anticipated operating conditions, which we used to see, and is still seen in some instances abroad. Due to CAFE, this is not possible, the oil that the CAFE qualification was run on must be the spec lubricant IIRC.

Subsequently, we've witnessed the introduction of thermal castration mechanisms that limit specific output if oil temperature gets too high. We've seen more widely the use of heat exchangers to control oil temperature and we've seen the mechanical design changes I've noted to the engines themselves to ensure that they'll survive properly on thinner lubricants.

None of that means that an engine is going to die prematurely on 0w-20 or 5w-20. It may mean slightly better wear performance if one were to do a tear down while running an xW-30 or xW-40, but that may be of zero consequence over the useful life of the equipment. We've had this discussion before. The other side of "better than" is not a pile of failed engines. We are talking what is likely a marginal improvement over what is already acceptable. It has to be acceptable, because it's what is spec'd for the expected lifetime of the equipment. And these improvements are likely only in certain areas.

Also, there is the drive for and expectation of universal lubricants which is why 0w-40 has become so popular for performance applications. The aforementioned lubricant chart can be greatly decreased in complexity due to the availability of these broad spread oils. Ergo, the Corvette has spec'd 5w-30 and 15w-50 and now 0w-40, Ford got away with just spec'ing 5w-50 but could have done a 5w-20/5w-50 recommendation. FCA went with 0w-40. The 5.7L HEMI has also simultaneously spec'd 5w-20 and 5w-30 depending on application. Without CAFE the former would have perhaps spec'd both.

We still see some of this verbiage hinted at in some manuals where there is a remark that a heavier lubricant may be preferable when towing for example or something similar. But it's not a requirement; it can't be for an application for which CAFE credits are claimed. Without that requirement you'd likely see less ambiguous language.


Overkill, thanks for summing up all the arguments about CAFE and thick vs thin in once concise and intelligent post! You've said here what I've been trying to say for some time....

This is just one of many reasons why I dropped the 20 grade oil for 30 in both my Jeeps. There are many people that are experts I was fortunate enough to speak with which made the decision quite easy for me.

 

[tig1]

Originally Posted by demarpaint
Originally Posted by JLTD
Originally Posted by OVERKILL


Engineers don't write owners manuals, can you imagine the disaster they would be if they did?

However, if Engineering input was freely allowed into what you received you would still see a range of viscosities recommending what's ideal for the anticipated operating conditions, which we used to see, and is still seen in some instances abroad. Due to CAFE, this is not possible, the oil that the CAFE qualification was run on must be the spec lubricant IIRC.

Subsequently, we've witnessed the introduction of thermal castration mechanisms that limit specific output if oil temperature gets too high. We've seen more widely the use of heat exchangers to control oil temperature and we've seen the mechanical design changes I've noted to the engines themselves to ensure that they'll survive properly on thinner lubricants.

None of that means that an engine is going to die prematurely on 0w-20 or 5w-20. It may mean slightly better wear performance if one were to do a tear down while running an xW-30 or xW-40, but that may be of zero consequence over the useful life of the equipment. We've had this discussion before. The other side of "better than" is not a pile of failed engines. We are talking what is likely a marginal improvement over what is already acceptable. It has to be acceptable, because it's what is spec'd for the expected lifetime of the equipment. And these improvements are likely only in certain areas.

Also, there is the drive for and expectation of universal lubricants which is why 0w-40 has become so popular for performance applications. The aforementioned lubricant chart can be greatly decreased in complexity due to the availability of these broad spread oils. Ergo, the Corvette has spec'd 5w-30 and 15w-50 and now 0w-40, Ford got away with just spec'ing 5w-50 but could have done a 5w-20/5w-50 recommendation. FCA went with 0w-40. The 5.7L HEMI has also simultaneously spec'd 5w-20 and 5w-30 depending on application. Without CAFE the former would have perhaps spec'd both.

We still see some of this verbiage hinted at in some manuals where there is a remark that a heavier lubricant may be preferable when towing for example or something similar. But it's not a requirement; it can't be for an application for which CAFE credits are claimed. Without that requirement you'd likely see less ambiguous language.


Overkill, thanks for summing up all the arguments about CAFE and thick vs thin in once concise and intelligent post! You've said here what I've been trying to say for some time....

This is just one of many reasons why I dropped the 20 grade oil for 30 in both my Jeeps. There are many people that are experts I was fortunate enough to speak with which made the decision quite easy for me.

And I went from a 5-30 to 0-20 on the advise of several posters here that have done the same with engines clocking 300K and beyond. With aprox 475K using 20- wt. in my last 3 engines, all is well.

 

[4WD]

Remember back when you had a small block with "four bolt mains" and that was a prized block ... similar sized aluminum blocks use 4 bolts plus cross bolts these days ...