# SAE Paper on Engine Wear with 20 wt. oil

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The one single compelling colossal metric that convinced me to be in the "thick crowd" is the HTHS wear graph which shows running any oil lower than HTHS 2.6 (0W-20) results in exponentially higher engine wear.

Please let us know why the ultra thin crowd ignores this metric and why you feel this metric is not important.

If you are concerned about engine wear at engine startup, 0W-8, 0W-16, 0W-20, 0W-30, and 0W-40 all have the same thin viscosity at engine startup. So the focus of this discussion should be engine wear at temperatures higher than 100C (212F) and why a thin oil is beneficial during high temperature, high RPM, high sheer, heavy load conditions. Typically the coolant temperature is around 100C in most cars during normal operation, but the bearing temperatures can go much higher (as high as 150C). In this scenario, all oil becomes thinner due to the heat, and there is a danger of metal on metal contact when the film thickness gets too thin. So that is why using a HTHS oil >= 3.2 is beneficial, and 3.5 being optimal. This gives a cushion of protection when the oil sheers to the next lowest grade as the oil ages during an oil change interval.
They say that a 0W20/0w30/0W40 have the same cold viscosity. Unfortunately, this is wrong. A 0W40 is about three times as thick as a 0W20 at -5/0/5/10C. If I start an engine at 10C with a 0W40 then it is about as if I start the car with a 0W20 at -10C. There are already considerable differences.

Over half of the allotted engines for the season have to last and be used for two full race weekends (practice, qualifying, race). Bottom line is 20W oils are what is used in these harsh conditions. Slightly heavier oils are used for break-in, using special break in oils.
When they need every advantage in competition and they're going to rebuild it every couple of weekends then yes it may make sense to sacrifice wear for a bit more performance with the xw20 oils.

The one single compelling colossal metric that convinced me to be in the "thick crowd" is the HTHS wear graph which shows running any oil lower than HTHS 2.6 (0W-20) results in exponentially higher engine wear."

This is likely where that graph originally came from. You may want to investigate further.

Ali

They say that a 0W20/0w30/0W40 have the same cold viscosity. Unfortunately, this is wrong. A 0W40 is about three times as thick as a 0W20 at -5/0/5/10C. If I start an engine at 10C with a 0W40 then it is about as if I start the car with a 0W20 at -10C. There are already considerable differences.
Who’s “they”, and where do “they” say that a 0w20 and a 0w40 are the same? You yourself just pointed out conditions where they could be the same…

Who’s “they”, and where do “they” say that a 0w20 and a 0w40 are the same? You yourself just pointed out conditions where they could be the same…
It is just more misunderstanding about what the winter rating means, and what it does not mean.

„Wenn Sie sich Sorgen über den Motorverschleiß beim Motorstart machen, haben 0W-8, 0W-16, 0W-20, 0W-30 und 0W-40 alle die gleiche dünne Viskosität beim Motorstart“ .
That comes from Bill7.

This statement is wrong, that's what I meant by my comment.

For me, any "faster" cold start is advantageous, even at 0 or 10C. It has been proven that the main wear in the engine in cold start is 70%.

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For me, any "faster" cold start is advantageous, even at 0 or 10C. It has been proven that the main wear in the engine in cold start is 70%.
Not exactly. It’s shown that low RPM, low load warmup is not significant. It’s high RPM, high load conditions before the oil has warmed enough that the AW additives start working.

The starting process alone until the oil has arrived at every point where it should be, the wear is higher than when 200 kilometres of highway. Can also be read in textbooks about the function and operation of an internal combustion engine, among other things.

"Not exactly. It’s shown that low RPM, low load warmup is not significant. It’s high RPM, high load conditions before the oil has warmed enough that the AW additives start working."

Incorrect. Read this paper and you will learn something:

Ali

You misunderstand me. It has nothing to do with speed at the very beginning. When I start the engine and it is completely cold, then the engine runs minimally "dry", depending on how quickly the oil is conveyed at the lubrication points. This moment is the high wear, not what comes after when driving.

The starting process alone until the oil has arrived at every point where it should be, the wear is higher than when 200 kilometres of highway. Can also be read in textbooks about the function and operation of an internal combustion engine, among other things.
Yea and since film thickness prevents wear then you want the oil to be thick. Which all oils are when they are cold.

I’m not sure where people get the notion for this “new physics” that they are trying to promote.

Maybe. This is the chart for my Toyota 2.5 in Australia. Basically you can run anything you like.

Also, in the USA it says you may use 0W-20 if 0W-16 is not available, but you MUST change it back to 0W-16 in 5000 miles - at the next 6 month service interval - rather than the specified 10K interval - or your car will self destruct (well I added the last part, couldn't resist) They give no such warning in Australia.

There are enough thin vs thick arguments on this board that I don't think we need anther, but I think you can infer from this at least that the engine oil viscosity has to do with a lot more than simply lubrication.

I personally don't have an issue running 0w-16 in my engine, but do prefer 0W-20.

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Good info. All I need to know for my 2.5 Camry. Thanks!

Think of viscosity like a pair of gloves. You could potentially try on 5 pairs, each in S, M, L or XL. Within each size, some may run a bit bigger or smaller. You could fit your hand in almost all of them, but some would be the perfect fit.
Where were you during the OJ trial?

"Not exactly. It’s shown that low RPM, low load warmup is not significant. It’s high RPM, high load conditions before the oil has warmed enough that the AW additives start working."

Incorrect. Read this paper and you will learn something:

Ali
Ali said:
Conclusions, and there were a handful as this was a very far reaching study:

Steady state wear is very low except when changing to high load and RPM conditions, the rise is moderate. I think they used the word insignificant for wear at steady state and low loads.

Is startup and idle (like on a remote start) not essentially steady state, low load? Isn’t this essentially how you claim you use 0w5 in your Navigator? Just wondering how you say this theory applies to your vehicles but not to others…

Yea and since film thickness prevents wear then you want the oil to be thick. Which all oils are when they are cold.

I’m not sure where people get the notion for this “new physics” that they are trying to promote.
The faster a layer thickness there is, the faster it can protect. Therefore, I already wrote that a thinner oil is three to four times thinner in the cold state and thus flows faster, that is physics.

The faster a layer thickness there is, the faster it can protect. Therefore, I already wrote that a thinner oil is three to four times thinner in the cold state and thus flows faster, that is physics.
And thicker oil is less likely to have left the bearing surface in the first place… besides, when we’re talking in the primary galleries, where oil does not “free flow” back to the pan, positive displacement pumps work under the “flow= rpm x pump displacement cubic inches / 231” correct?

You’ll note viscosity does not factor into the equation when you are working on the outlet side of a PD pump. Thick or thin, a PD pump is going to move a specific volume of oil for every revolution. The psi will be higher in the oiling circuit with a thicker oil, and will increase with RPM. As long as you don’t cavitate on the pump inlet side, as far as main & rod bearings along with lifters go, they should get the same amount of oil regardless of viscosity. It’s the pushrod tips, and timing chains, and valve springs that get indirect oiling that would see slower lubrication with a thick oil in cold weather. But again, the thick oil will still have left more oil present on those surfaces.

The only “advantage” that you can really attribute to thinner cold oil is reduced HP to turn the oil pump, I’ll give you that. And that’s what manufacturers and CAFE are chasing. If an oil pump takes, say 10HP to turn with a cold 10w30 and only 4HP to turn with a 0w20, that’s 6HP worth of fuel you don’t need to burn, and that’s where the CAFE requirements come in to eke out their minimal gains. Has nothing to do with longevity or protection; a thinner oil simply takes less power to turn the oil pump. That is physics.

And just because the "thicker" oil is 3-5mm2 thicker when warm, does it stay in the storage centres and the thinner one does not? Sorry, that's ridiculous to say that, for example, 13mm2 stays longer in the warehouse and on the surfaces when the engine is switched off than an oil with 7mm2, absolutely ridiculous.

An oil lives through the shear in the fluid. There are some oils today with viscosity-dependent production capacity. And you still say that the same oil film or Stability is given in the cold, no matter what viscosity? Many also think that the higher the oil pressure is, the better, but it depends on why an oil pressure is high. With narrowed channels due to deposits, I can have a high oil pressure, but still possibly too little oil in the right place.

Furthermore, I am aware of almost no cases today where thin oils caused premature wear. Even the European manufacturers have this under control very well. If thin oils are so bad for wear, then the Japanese in particular have had to exchange engines weekly for two decades. And what happens? Nothing. My honda dealer has had engine damage for 30 years, they have been using only 0W20 for 18 years now. The new a45 amg also uses only 0W20. And nothing will happen there in the future either. The thin oils not working is more the problem in the minds than in practice.

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and for good measure: the Stribeck curve

And just because the "thicker" oil is 3-5 CP thicker when warm, does it stay in the storage centres and the thinner one does not? Sorry, that's ridiculous to say that, for example, 13mm2 stays longer in the warehouse and on the surfaces when the engine is switched off than an oil with 7mm2, absolutely ridiculous.
You need to learn how an engine works. And how oil works.

You need to learn how an engine works. And how oil works.
I think I have the understanding to say that the above example does not apply, is simply physics

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