Spun rod bearing..

[turbo50]

5/50w vs 20/50..Anyone know the difference ?

The first number is the weight for when the oil is cold

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[Roh92cp]

Thin oil flows better moves faster through the motor promoting better cooling of parts that get extremely hot like rod and crank bearing. It's not the thickness of the oil that prevents shear, but rather the durability of the oil film and that has everything to do with the additive packages. A properly designed oil can provide the highest shear protection even at the thinnest viscosities.

 

[Roh92cp]

Here is some information regarding oil viscosity and its effect on shear protection. This is from the motor oil engineering test data from the 540ratblog.
https://540ratblog.wordpress.com/2013/06/20/motor-oil-wear-test-ranking/

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29. Eliminating BMW M3/M5 Rod Bearing Failures
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The BMW M3/M5 models have had an ongoing problem with rod bearing failures for a number of years now. The M3’s S65 V-8 engine was derived from the M5’s S85 V-10 engine. They share the same basic architecture and aluminum construction.
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And I was asked if I could offer a recommendation on how to deal with this problem, by reviewing a comprehensive rod bearing failure thread on the M5Board Forum with many, many failed rod bearing pictures as well as additional supporting data, which also included an M3 link to extensive engine tear down inspection/examination data, as well as additional M3/M5 information and data. This is an enormously long Forum thread (it had reached nearly 70 pages when I was looking at it) that was started in 2013 and was still going in 2016.
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After going through all that, it turned out that the root cause of all those failures was that BMW had designed/built the engines with insufficient rod bearing clearance (barely large enough for 5W30 motor oil and WAY too tight for super thick oil), insufficient connecting rod side clearance, and they called for insanely thick 10W60 motor oil, which is WAY too thick for acceptable oil flow/lubrication/cooling. It was a perfect storm of doing multiple things completely wrong to actually “cause” rod bearing failures. It was extremely disappointing to see BMW do such a poor job at designing/building those engines. They actually unintentionally designed the engines so that the rod bearings “would” fail. I would have expected far better from them.
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It was noted that along the way since all this began, that BMW has increased the rod bearing clearance a little, and now also allows the use of thinner oil (though many owners still seem to think they should use super thick oil for protection). But, there was no mention of them increasing the rod side clearance, which needs to be correct in order for oil to properly flow through and out of the rod bearings to provide the critical lubrication and cooling they need to survive.
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For owners of one of these models, there isn’t a lot most of them can do about the rod side clearance problem, or about the rod bearing clearance issue that their particular model year may have, unless they tear down the engine and have it rebuilt correctly. However, there is one thing owners can easily do to significantly help with this problem.
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First of all, everyone needs to understand that motor oil “viscosity” is NOT what determines wear protection. That is just an old MYTH, which some people who don’t understand anything about motor, still believe. So, ignore anything you’ve been told about needing thick oil for wear protection, because using thick oil is one of the worst things you can do to your engine.

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Consider the following:
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Below is actual motor oil viscosity test data that came out of my Engineering Tests on Motor Oil film strength/load carrying capability/shear resistance:
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20 wt oils rank between number 3 and 176
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30 wt oils rank between number 1 and 187
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40 wt oils rank between number 16 and 175
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50 wt oils rank between number 26 and 184
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The one 60wt oil tested ranked 74th out of 187
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So, as you can see, the various oil viscosities all overlap each other regarding their wear protection ranking position, which clearly shows that oil viscosity does NOT play a role in an oil’s wear protection capability. An oil’s wear protection capability is determined by its base oil and its additive package “as a whole”, with the primary emphasis on the additive package, which contains the extreme pressure anti-wear components. And that has nothing to do with viscosity.
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Oil “flow” is lubrication, and using thicker oil will simply reduce critical oil flow for no good reason. Plain bearings, such as rod and main bearings, are components that are not designed to be lubricated just by an oil film, they are designed to be lubricated by a flow of liquid oil. Keep in mind that oil pressure is NOT what keeps these parts separated. Oil pressure is a measurement of resistance to flow, and the pressure only serves to supply/move the oil to the clearance between the bearings and the crankshaft journals, and of course to move oil throughout the entire engine. The crankshaft journals and its bearing shells are kept separated by an incompressible hydrodynamic liquid oil wedge that is formed as the liquid oil is pulled in between the spinning parts. All liquids are incompressible (that’s how hydraulics work, including brakes with their watery thin brake fluid), so it does NOT matter what the viscosity of any liquid is. Thick oil or thin oil will create the same incompressible liquid oil wedge.

 

[daniel_94kg]

Sorry to hear about your motor. Mine spun #5 rod bearing back in March. Basically same thing, just not at the track. I had changed the oil (Mobil 1 5w20 like I had always been using), took it out a couple days later, pulled onto the highway and that was that. I ended up getting a new block and forged internals. Now my car hasn't seen over 4000 rpm since June, but it hasn't been driven. I don't ever plan on taking mine past 7000rpm anymore to be honest. Hope you get it fixed up and back out soon.

 

[Excelerater]

The first number is the weight for when the oil is cold

Correct,thats why drag motors run 20/50 . You made my point
and thats also why 5/50 is used on that 8500RPM GT350.
Thicker oil cools better and offers better protected under severe conditions

Here is some information regarding oil viscosity and its effect on shear protection. This is from the motor oil engineering test data from the 540ratblog.
https://540ratblog.wordpress.com/2013/06/20/motor-oil-wear-test-ranking/

.
.
Oil “flow” is lubrication, and using thicker oil will simply reduce critical oil flow for no good reason. Plain bearings, such as rod and main bearings, are components that are not designed to be lubricated just by an oil film, they are designed to be lubricated by a flow of liquid oil. Keep in mind that oil pressure is NOT what keeps these parts separated. Oil pressure is a measurement of resistance to flow, and the pressure only serves to supply/move the oil to the clearance between the bearings and the crankshaft journals, and of course to move oil throughout the entire engine. The crankshaft journals and its bearing shells are kept separated by an incompressible hydrodynamic liquid oil wedge that is formed as the liquid oil is pulled in between the spinning parts. All liquids are incompressible (that’s how hydraulics work, including brakes with their watery thin brake fluid), so it does NOT matter what the viscosity of any liquid is. Thick oil or thin oil will create the same incompressible liquid oil wedge.

True but thicker oil offers better shock and cooling protection ,this is why its used in racing

 

[SolarFlare]

Correct,thats why drag motors run 20/50 . You made my point
and thats also why 5/50 is used on that 8500RPM GT350.
Thicker oil cools better and offers better protected under severe conditions






True but thicker oil offers better shock and cooling protection ,this is why its used in racing

In engines designed with slightly more tolerances to allow that thicker engine flow. Mustangs run best at 30w unless specifically designed to run thicker. A racing motor designed to run thick oil at high RPMs and high temps has no problem running said oil. Throwing 40w or 50w oil on a coyote that doesn't see constant high RPMs/high oil temps while at the same time putting a reische 170* t stat and lowering fan settings to come in early is just a downright silly combination.

 

[dubster99]

You guys with spun rod bearings...how much damage did you end up having?

 

[daniel_94kg]

You guys with spun rod bearings...how much damage did you end up having?

Spun # 5 rod + 2 mains were starved of oil. I shut mine off immediately and barely ran it after having the issue. My block needed to have the mains line bored, but I got lucky and have a spare block now.(Ito in my storage shed waiting on a rainy day/possibly sell). Also, I had my crankshaft ground and reused it. .

 

[Roh92cp]

Correct,thats why drag motors run 20/50 . You made my point
and thats also why 5/50 is used on that 8500RPM GT350.
Thicker oil cools better and offers better protected under severe conditions






True but thicker oil offers better shock and cooling protection ,this is why its used in racing

Not sure I can agree with your statements, but that's OK. I think if you read further in what I posted above you will see it contradicts what your saying. Anyway :cheers:

 

[HaximusPrime]

So I'm going to chime in here as a non-oil expert just to repeat some things I've read after researching this a few days. You all are free to refute or reject them them, in fact I encourage you to so I learn more:

- Too many people say "thicker oil protects better" because it keeps oil pressure up. In reality, more oil pressure doesn't mean more flow, it means less. Less flow isn't something you necessarily want when you're running hotter.
- Apparently our motors (valve?) clearances are designed specifically for 20 weight oil, so using thicker oil actually messes with the tolerances and therefore the tune. I would guess this isn't a problem if you're custom tuning anyway?
- 5wXX is actually a bit thicker than 0wXX at operating temperature because of the additives that make the oil flow better at cold start.
- Most wear for normal driving conditions actually occurs during cold start, which is why 5w is recommended over 0w.


Thoughts?

 

[Roh92cp]

You guys with spun rod bearings...how much damage did you end up having?

My OPG failure starved 2 rod bearings, the rest of the motor was fine including the heads. Only had superficial wear on 3 of the head bearing caps. Block was fine, but crank according to MMR would cost as much to repair it as to buy a new crank. I ended up getting a new long block.

 

[Roh92cp]

So I'm going to chime in here as a non-oil expert just to repeat some things I've read after researching this a few days. You all are free to refute or reject them them, in fact I encourage you to so I learn more:

- Too many people say "thicker oil protects better" because it keeps oil pressure up. In reality, more oil pressure doesn't mean more flow, it means less. Less flow isn't something you necessarily want when you're running hotter.
- Apparently our motors (valve?) clearances are designed specifically for 20 weight oil, so using thicker oil actually messes with the tolerances and therefore the tune. I would guess this isn't a problem if you're custom tuning anyway?
- 5wXX is actually a bit thicker than 0wXX at operating temperature because of the additives that make the oil flow better at cold start.
- Most wear for normal driving conditions actually occurs during cold start, which is why 5w is recommended over 0w.


Thoughts?

I would agree and so would the engineering oil data from the report I posted. About most of what you have said. The 5wXX to 0wXX weight oil being thicker at running temp is somewhat true but there are variables and it would be minimal.

Here is a quote from the oil test about oil viscosity, pressure and its effects.

" Oil “flow” is lubrication, and using thicker oil will simply reduce critical oil flow for no good reason. Plain bearings, such as rod and main bearings, are components that are not designed to be lubricated just by an oil film, they are designed to be lubricated by a flow of liquid oil. Keep in mind that oil pressure is NOT what keeps these parts separated. Oil pressure is a measurement of resistance to flow, and the pressure only serves to supply/move the oil to the clearance between the bearings and the crankshaft journals, and of course to move oil throughout the entire engine. The crankshaft journals and its bearing shells are kept separated by an incompressible hydrodynamic liquid oil wedge that is formed as the liquid oil is pulled in between the spinning parts. All liquids are incompressible (that’s how hydraulics work, including brakes with their watery thin brake fluid), so it does NOT matter what the viscosity of any liquid is. Thick oil or thin oil will create the same incompressible liquid oil wedge "

 

[Lonmon]

Anyone know if the GT350 has different rod and main bearing clearances from the GT. Just curious because I was recommended by my tuner to run 5w50 for high rpm operation (shifting at 7800 rpm). I was going to make the switch knowing that the GT350 runs this oil as a factory fill. I may change my mind if the GT350 has tolerances specifically set up for this oil. Maybe just bump to 5w30 instead. I would imagine the tolerances are virtually the same though.

 

[turbo50]

I can post up pic of my old bearing while running 20w50 shifting at 7800rpm and 730whp they look brand new. Every car I built or boosted ran 20w50 amsoil and in the winter I ran 5w50

 

[F1scamp]

Well I finally spent a little time to look into the motor. Works been crazy and I just didn't want to know if I was going to need heads. lol
It's been sitting on the engine stand for a couple months... I pulled the valve covers off and pulled cam caps. Driver side look perfect. One journal on the p/s has a slight groove in the cap you can barely feel with your fingernail, nothing on the cam. No discoloration or signs of oil starvation. I don't see any reason not to run them. I am leaning towards throwing a factory short block in it and cleaning the piss out of everything else. Hard to beat the price of them, and since I have already been kicked off the track a few times already, arguing needing more power is alittle moot. Havent pulled the cover to check the oil pump gears yet. No real rush since its winter in NY.

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