Low Viscosity Effect on Heavy Duty Engine Components

[nap]

Originally Posted by ZeeOSix

Lots of miles (km) on those oil runs - and the wear deviation starts showing up after 10 km. Did they take KV100 and HTHS readings as the miles piled up to see if the 10W-40 sheared down below the 5W-30? Lead wear would be journal bearings I would assume.

The explanation offered by the authors is "The most feasible explanation could be linked to additive depletion. For oil B, after 20,000 km anti‐wear additives have been almost absolutely depleted (FT‐IR measurements have been performed to assess this situation) and an acidic attack against Babbitt metals appears leading to the situation previously mentioned. In the case of the LVO, the higher content of anti‐wear additives, let to obtain a longer period of usage where this corrosive wear is under control, obtaining very low lead wear rates." Which may lead someone to be cautious with the latest iterations of consumer oil standards....

 

[Shannow]

nap, really good dot point that...additives at work. It's consistent with the start-up wear statements here https://www.sae.org/publications/technical-papers/content/600190/ Predominantly corrosion, not "flow" I've posted stuff on hastening warmup before, think this, but will have to scout through the library over the weekend. https://www.sae.org/publications/technical-papers/content/2011-01-0318/ (But suffice to say that thicker oil will heat faster...LOL)

 

[Silk]

So, would the oil heat up faster in say a 7 bearing 6, as opposed to a 3 bearing crank 4 cyl of similar capacity ? Of course the 4 cyl is going to have larger journals which could just make it the same anyway.

 

[Shannow]

Would say so...look at the bottom end of a slant 6, or 4 main ford versus the 7 bearings, and the mains aren't materially larger in total dimension than the 7s. But the piston skirt area is a pretty big "bearing" area for heat to e generated, diminishing the effect of the mains.

 

[CR94]

Uh ... haven't 4-bearing in-line Sixes been obsolete for a very long time (a little less long for the Slant Six)? 3-bearing in-line Fours, too? GM, Ford, and AMC all switched to then-new 7-bearing Sixes in the early- to mid-1960s in the US.

 

[Shannow]

Was still a valid question, worth answering...

 

[Silk]

In my mind I had a 149 Holden and a large British 4 cyl...large BMC, Rootes and Standard were still made at that time the 7 bearing Holden came out. There just seems to be a lot more going on in an inline 6 than a 3 bearing 4 to heat up oil. What's obsolete got to do with anything ?

 

[Cujet]

Decades ago, engineers learned that direct measurement was required when testing wear rates. UOA's, while helpful, do not reflect individual wear rates. I worked for Mobil OIl in their flight department. I worked with the Mobil engineers on SHC100 grease testing and on Mobil 245 turbine engine oil. This was real world testing on Mobil Oil's flight department fleet. With very specific testing protocols. The scanning electron microscope and other forms of very precise measurement were the best ways to determine wear rates. I was a young guy and always found time to chat with the engineers about the processes and results. It was amazing to see how they could accurately determine bearing wear rates on perfectly serviceable bearings. What we consider UOA; mass spectrometry, was interesting information, but did not reflect real world wear, and especially wear of individual components.

 

[Jetronic]

Originally Posted by Shannow

I've posted stuff on hastening warmup before, think this, but will have to scout through the library over the weekend. https://www.sae.org/publications/technical-papers/content/2011-01-0318/ (But suffice to say that thicker oil will heat faster...LOL)

EGR coolers do this, and then we have in nearly all turbocharged engines and oil/coolant heat exchanger. The heat exchangers have limited capacity of course, but every Watt helps during warm-up.

 

[Gokhan]

It's interesting that they didn't encounter any problems in the bearings with the low-viscosity oil. My understanding is that the ring wear is determined by the base-oil viscosity (including the additive package), not the HTHS viscosity, the latter of which is raised by the VII. This is because it is primarily boundary lubrication. A 15W-40 has a much higher base-oil viscosity than a regular 10W-30. A better comparison would be to make a nearly VII-free 10W-30 with a high base-oil viscosity using synthetic base stocks and study that. Alternatively you can study a SAE 30 monograde oil. I bet you wouldn't see as much difference in the ring wear if you study a SAE 30 monograde or a nearly monograde SAE 10W-30.

 

[LubricatusObsess]

This was also my understanding from lubricant chemistry training. Is this not the case in the field or other test lab results?

 

[bulwnkl]

This is an interesting read. Clearly, appropriate engine designs, coatings, and finishes, along with newest-tech oils, can let us use lower-viscosity oils in engines without compromising durability. In fact, those combos _may_ allow improved durability, at least of some components. Question: If (when) those designs, coatings, and finishes in the engines, combined with newest-tech fluids, are used in conjunction with ‘traditional' oil viscosities, do the higher viscosity fluids still show durability advantages?