What Is the Perfect Oil Viscosity?

[AEHaas]

What is the perfect oil viscosity and why? We should invent an oil that did not thin under shear stress and was temperature independent. You would think that chemists would be working on this. The oil would not thicken after the engine was turned off. It would be the same at - 25 F and 250 F. On the race track and within a hot bearing it would not thin. It would be the perfect oil. I would pick a viscosity of 5 cS for the average automobile. It would be thick enough to prevent wear in a hot bearing and thin enough to have the best flow rate. I wonder though if a thinner oil yet would be best for true racing situations to allow for additional flow and cooling. aehaas

 

[novadude]

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You would think that chemists would be working on this.

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I suspect it is not so easy to economically make such a potion. Getting people to pay more than $5 / qt would be a hard sell.

 

[Curious Kid]

How nice that would be, resulting in decreased start-up wear, reduced emission for those of us that see a lot of short trips...and in just having another "problem" solved. The costs could be reasoned aside by the benefits, say very extended OCI. If shearing could be drastically decreased, than other areas of concerns would be additive/acid/corrosion/oxidation control... Premium oil filtration, oil analysis, and additive pack refreshment doses would replace compete oil changes, and would perhaps be done yearly at a minimum, like when you have your vehicle inspected. I see how this could take some power out of the average consumer in that things would become more technical and so forth and relying upon outside resources, but then again what isn't these days. Just a thought anyhow. PS - Thanks for the information packed site!

 

[Gary Allan]

I'm sure it exists ..at $4000/quart (net costs of R&D distributed over the quarts produced) ..or probably something close to it.

 

[farrarfan1]

Since the perfect oil may or may not be developed in most of our lifetimes what would be considered the closest to perfect that is currently available? Mobil 1 5W30? Schafefers 5W30? Delo 15W40?

 

[427Z06]

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Originally posted by farrarfan1: Since the perfect oil may or may not be developed in most of our lifetimes what would be considered the closest to perfect that is currently available? Mobil 1 5W30? Schafefers 5W30? Delo 15W40?

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Given the requirements in the topic post, I'd say RedLine 5w20, given it's published specs. 6.1 cSt @120°C 3.9 cSt @150°C HTHS 3.3 However, I equate the probability of original post ever seeing the light of day the same as Uncle Bill deciding to give me all his billions and then panhandling for spare change on the street corners of Seattle.

 

[JHZR2]

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Originally posted by AEHaas: We should invent an oil that did not thin under shear stress and was temperature independent

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The does not thin under shear stress may be doable, but the latter id say is a nice dream with hydrocarbon lubricants. v = A exp (Ev / k T) where v is the kinematic viscosity, k Boltzmann's constant, T the temperature, and A and Ev constants. Ev / k cant always fulfill the requirement that it, times 1/T = 0 (so that exp(0)=1 and viscosity is constant wrt T. Unless of course, the activation energy for viscous flow, Ev would be 0, and then the fluid would be, well, I suppose an ideal gas! Also you must consider the need for viscosity to change in an engine as the tolerances and clearances inside change due to thermal expansion. JMH

 

[rugerman1]

Perfect Oil Viscosity? The thinnest vis that establishes/maintains HYDRODYNAMIC LUBRICATION. ceteris paribus

 

[AEHaas]

Only 427Z06 was bold enough to give a number on this thread. On all other threads there are so many numbers given out. What is YOUR number, ceteris paribus? aehaas [ March 02, 2005, 01:52 PM: Message edited by: AEHaas ]

 

[rugerman1]

In his Speedtalk interview,Terry Dyson said start with a 30 weight oil and work from there.Terry has forgotten more about Tribology than I'll ever learn.

 

[JHZR2]

Since I'm being forced, I would say high 12s???? JMH

 

[Razl]

I'm embarrassed to say that I remember the time I believed a multi viscosity oil was thin when cold and thickened as it heated Wouldn't it be nice if there was an additive blended into the oil that would keep it thin at startup and then as it heats up, the additive evaporates from solution resulting in a thickening of the oil? Of course there would need to be an evaporation collection system (chemically or mechanically) to hold the additive until things cool back down. I wouldn't have the slightest idea where to begin!

 

[427Z06]

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Originally posted by rugerman1: In his Speedtalk interview,Terry Dyson said start with a 30 weight oil and work from there.Terry has forgotten more about Tribology than I'll ever learn.

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When was that on? Is it scheduled to be on again? Do you know if there's a video clip of this interview that you can download from the internet?

 

[rugerman1]

This is as much as I know: SpeedTalk Title: "Oil Analysis" Guest: Terry Dyson Length: 146 min. 2 CDs Show # 015 Broadcast Date: 7/11/03

 

[JohnBrowning]

Their is no perfect single viscosity. Antartica is going to have prefered deviation and Death Valley will have it's prefered deviation. Personely if the oil is not being consumed, has the reqired flow,pump and crank propertys, will maintain OEM recomended oil pressures at established temp and rpm settings and has an HTHS of at above 3 then the SAE viscosity is of little importance. I do prefer HTHS above 3.5 and some OEM's require that so that must be taken into account. So if a 5W20 does the above then go for it if you need a 5W40 or 15W40 then thats fine too! Reliase that minimums are just that if you want to add an additional margin for saftey increaseing the HTHS is the best way to go. This does not always have to mean a different SAE viscosity though! Their is enough variance in clearance to establish the need for different viscositys of oil. We also have drasticly different models of usuage. My wife driveing the kids 22 mile too and from school at 55MPH-25MPH durieng Michigan winter in a Toyota I4. This drasticly different from me driveing along at 200KPH for an hour and a half in a RUF 911 on the Autobahn! What if the wife is driveing a TDI in Arizona? I might be driveing a Slant Six Dart in Ga.! AEHass, While Redline 5W20 is impressive you would have to run it and do a UOA to see if it was going to work in the application! [ March 02, 2005, 03:00 PM: Message edited by: JohnBrowning ]

 

[Gary Allan]

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Their is no perfect single viscosity.

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Sure there is!! You just need a V1 of about 1100. What's so hard about that?

 

[AEHaas]

I spoke to Red Line's Dave just this morning. They are thinking of making a 5W-20 that is SM, GL-4 compliant. I told him that I would try it in all my cars. aehaas

 

[TallPaul]

I believe a silicon based (instead of hydrocarbon) lubricant would have very little change in viscosity over the temperature ranges motor oil typically is subject to. Aside from the high price (min probably 25 $ a quart) not sure if it would hold up well under the blowby contamination in automotive use. But I do think it is used in non combustion applications.

 

[JHZR2]

thats the perfect newtonian fluid! I believe rheometers are usually calibrated using that. JMH

 

[427Z06]

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Originally posted by AEHaas: I spoke to Red Line's Dave just this morning. They are thinking of making a 5W-20 that is SM, GL-4 compliant. I told him that I would try it in all my cars. aehaas

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Cool. If you talk to him again, please ask him to please not screw up the current version. It's one of my favorites for certain applications.