15w50 in Northern Yukon Canada.
Wear vs Viscosity
- Thread starter Al
- Start date
Yes due to the winter rating. You could use a 50-grade with an appropriate rating.
Running a 50wt in -60 ambient sounds like a great idea.
Still waiting to cash in on that bet.
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Yesh that's why you aim for 10cSt at 100c. No need to go thicker than around 10cSt at operating temperature.
Why not? Once it is warm then what is the real difference? Will it cause more wear?
And the bet has time yet. I am working on that longevity.
How is the “50” in 15w-50 relevant in that environment? First number matters there, second doesn’t care where it is.
There have been many threads discussing how more viscosity gives more wear protection due to more film thickness between moving parts. Viscosity and the resulting film thickness is the main thing what keeps moving parts from rubbing and wearing. When the film thickness goes to zero, the only thing left to help reduce wear is the AF/AW tribofilm, aka the "film strength" of the oil.
Turbo engines put more load into the rod and crank bearings, and they therefore often spec a higher viscosity to give more MOFT in those journal bearings to keep them more protected from wear.
I still recall some YouTuber who thought it would be a good idea to run the 5W-20 in his car (non-turbo) when he took it to track days because he thought it would help keep the oil temperature down (less shear heat). But what he did was trash the journal bearings. He should have used a thick xW-30 or a xW-40 instead. There's a reason manufacturer's say to use a thicker oil for track use, lol.
Shear friction from more film thickness is better than no film thickness and rubbing metal-on-metal friction.
You post this after wondering if there's ever been any studies relating viscosity to wear (post 1), lol. Yeah, it's been studied for over 100 years after it was discovered that viscosity correlated to film thickness (all other factors constant), which is the main factor that keeps moving parts separated and from wearing.
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Don't use the wrong W rating for the climate. The "50" grade (the KV100) doesn't matter in a cold start-up like that.
Doesn't sound like you understand the difference between the W rating and the KV100 grade rating. They are two separate things in a multi-viscosity oil.
10 cSt at 100C is around a typical 30 grade.
Depends on what your doing. If running a track car real hard, I'd want a xW-40.
10 cst is a lower limit for me, 15 overkill.
Patman
Staff member
I drive my Civic very gently, as MPG is my concern there so I’m completely comfortable with an oil that is around 8cst at 100c. I really don’t believe that I would benefit going thicker in the Civic because of my driving style. I rarely go above 50% throttle in this car and the engine spends 99% of its time at 1700 rpm or less. It simply doesn’t need that extra viscosity at all. On the other hand, I drive the Corvette differently and I like to go full throttle when I have a clear stretch of road so that is why I want an oil that is closer to 12 cst. I believe those choices are perfect for my driving style and will result in long engine life out of both cars.
Well viscosity is the most important part I would think. But oils are blended with many components, so the end product matters most. The stress levels used for the HTHS test are indicative of those in the bearings of engines. Stresses seen in the ring, bore or lifter are said to be higher.
Has nothing to do with the W rating. Oil won't get close to operating temp when ambient is -50.
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An oil is not going to get to operating temp when it's -50 ambient. Considering the KV of a 50wt is close to 20 at 100c, what is it going to be when the oil is only sitting at 75c?
But then again no oil will likely reach operating temperature at -50 which admittedly is an extreme condition not experienced by most individuals on this planet. So it’s a bit of an outlier.
Even then what is the detriment except greater fuel consumption? The thicker the oil the faster it will warm up anyway. A 50-grade oil is unnecessary at those temperatures and how many are using such oils in those areas? No harm will come to the engine as long as it can be pumped, and it will be as long as the winter rating is appropriate for the starting temperature.
You’re making a great deal out of something that clearly isn’t optimal but on the other hand won’t cause mechanical damage.
Even then what is the detriment except greater fuel consumption? The thicker the oil the faster it will warm up anyway. A 50-grade oil is unnecessary at those temperatures and how many are using such oils in those areas? No harm will come to the engine as long as it can be pumped, and it will be as long as the winter rating is appropriate for the starting temperature.
You’re making a great deal out of something that clearly isn’t optimal but on the other hand won’t cause mechanical damage.
Yeah running a car on the track the oil is likely getting a lot hotter than 100c and you would want something thicker so it's around 10cSt at operating temperature.
