Well said.
2021 Odyssey oil spec
- Thread starter MrStamper
- Start date
Long rods with long strokes in low deck-height engines that require super short compression heights don’t help either.
Take the Ford 302. Stock compression height about 1.6”, thick rings… no flutter and no consumption if good oils were run. Stroked & poked 347s have a comp height of 1.2” and thin rings and have oodles more issues with oil burning and ring flutter.
sure makes stocking oil easy
MolaKule
Staff member
Clearances and Tolerances:There is such a thing and it's constantly being confused with 'tighter clearances'. Presumably GM's issue is at least in part due to loose tolerances, not loose clearances.
https://www.epi-eng.com/mechanical_engineering_basics/clearance_and_tolerance.htm
This was from 2005 from an old Toyota R&D article I had posted 20 years ago:
"Lowering the viscosity of engine oil is effective in reducing the fluid friction. However, it decreases the oil film thickness, and causes the increase in the wear of engine parts. Through the engine wear tests using an radioisotope tracer technique, it was clarified that an HTHS viscosity of 2.6 mPa¥s was the lower limit to prevent the increasing wear. It was also found that the influence of the lowering viscosity on the wear of piston rings was larger than that on the wear of the cams and connecting rod bearings.
Addition of friction modifiers is effective in reducing the friction under boundary lubricating conditions. MoDTC was determined as an excellent friction modifier, after evaluating its effects on the friction of valve train and on the fuel consumption of engine. The effect of MoDTC on the friction reduction was considered to be caused by both of the MoS2 film formed and the rubbing surface smoothness that decreased the metal contact.
From the results of these investigations, it was concluded that the points of designing low friction engine oil were lowering the HTHS viscosity to 2.6 mPa¥s and the addition of MoDTC. Based on this guideline, a low friction engine oil has been developed, and it contributes to the improving fuel consumption of automobiles."
"It is also important to note that, contrary to what many take for granted, higher viscosity in and of itself does not translate into better engine protection. Extensive testing has shown the opposite to be in fact true. As long as a lower-viscosity oil is formulated to resist evaporation and provide high film strength, this lighter oil will actually deliver more complete protection to the engine parts, since its more rapid circulation delivers both better lubrication per se, and far better cooling characteristics…a critical advantage, given that oil flow furnishes up to 30%"
"Lowering the viscosity of engine oil is effective in reducing the fluid friction. However, it decreases the oil film thickness, and causes the increase in the wear of engine parts. Through the engine wear tests using an radioisotope tracer technique, it was clarified that an HTHS viscosity of 2.6 mPa¥s was the lower limit to prevent the increasing wear. It was also found that the influence of the lowering viscosity on the wear of piston rings was larger than that on the wear of the cams and connecting rod bearings.
Addition of friction modifiers is effective in reducing the friction under boundary lubricating conditions. MoDTC was determined as an excellent friction modifier, after evaluating its effects on the friction of valve train and on the fuel consumption of engine. The effect of MoDTC on the friction reduction was considered to be caused by both of the MoS2 film formed and the rubbing surface smoothness that decreased the metal contact.
From the results of these investigations, it was concluded that the points of designing low friction engine oil were lowering the HTHS viscosity to 2.6 mPa¥s and the addition of MoDTC. Based on this guideline, a low friction engine oil has been developed, and it contributes to the improving fuel consumption of automobiles."
"It is also important to note that, contrary to what many take for granted, higher viscosity in and of itself does not translate into better engine protection. Extensive testing has shown the opposite to be in fact true. As long as a lower-viscosity oil is formulated to resist evaporation and provide high film strength, this lighter oil will actually deliver more complete protection to the engine parts, since its more rapid circulation delivers both better lubrication per se, and far better cooling characteristics…a critical advantage, given that oil flow furnishes up to 30%"
Most xW-20 are around 2.7 HTHS. Add in some fuel dilution, some shear and you are under 2.6 very quickly.
My 2015 Acura doesn’t have vcm, yes I’m a thickies. Only time the engine makes power is 3800-7000. Yes I much rather have a HTHS >3.5. The S2K when it first came out had a redline of 9200. Honda recommended 10/30. They had some valve spring issues running that high rpm
In the case of GM it could very well be a design issue, however it is also possible bumping up to a 40 grade could save them a ton of money in warranty claims. If that wasn't the case they would have never considered bumping up to a 40 grade, and bringing a lot of vehicles to do so. So imo there is something about viscosity playing a role in protecting an engine better than the CAFE thin oil push. Time to hide again.
Show of hands...
How many Hondas are on the road still with a lifetime of 0w20.
How many production engines are more power dense than the M139 which specs a 0w20. Ps thats 208 hp/liter. The new zr1 is sub 200.
How many Hondas are on the road still with a lifetime of 0w20.
How many production engines are more power dense than the M139 which specs a 0w20. Ps thats 208 hp/liter. The new zr1 is sub 200.
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What would also help is sticking to Chrysler's oil specs that target valvetrain wear in their engines specifically.
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Extend the logic. Why not 10w-60?
Is it thicker is better, or is it run the minimum viscosity oil that reliably maintains oil pressure?
Is it thicker is better, or is it run the minimum viscosity oil that reliably maintains oil pressure?
Yes, but will it make a noticeable difference between 5w-30 vs 0w-20
That’s not how it works
Wasn’t 15w50 the recommended grade for Corvettes on track days?
A high viscosity option instead of 0w40 in the 6.2L is 5w50.
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Bearings aren't supported on oil pressure. The oil pressure replenishes oil squeezed out. Too thin results in lower pressure because the flow can't keep up, resulting in a bearing no longer supported.
Pistons and cylinders are lubed with crankcase mist. Thinner oil makes more mist.
The rest, such as rocker tips or valve caps, are splash lube. Thinner oil gets between the surfaces better.
Thicker oil results in less lubrication and more parasitic losses.
You want the "minimum maximum". Minimum viscosity to replenish the journals. That's how it works. The boundary layer breaking down to allow metal-metal contact, assuming sufficient oil supply, is dependent on other factors than viscosity.
Track days the oil gets hot. Higher viscosity to offset the thinning due to heat.
Obviously GM has discovered that their engines have hotspots where the oil gets too thin. Viscosity, pressure, flow. That's all. It's not that thicker oils protect better on their own. Thicker oils only protect better if it's a high heat zone where viscosity decreases to the point that oil is squeezed out at a higher rate than can be replenished.
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It's the lower rod bearing that is having the problem which I've never seen. After thinking on this for a while I'm thinking the clearance in the lower bearing is out of spec. Closer to the crank than the upper bearing starving the lower bearing from adequate oil circulation.
My 2017 Hyundai Theta II 2.4L had 5W20 in the sump when new and I used QSUD 5W20 for one OCI before switching to 5W30 (allowed by Hyundai in USA OM). The engine ran a bit more free with 20 weight oil but quieter with the 30 weight oil .Do nothing OR Hail Mary, with hope.
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