Are thinner oils about fuel economy or tighter engines?

[ZeeOSix]

Its proof of concept of flow through a screen. Isn't gravity one of the methods to test viscosity, you know the ball drop in the tube?
And besides many engines now use a variable displacement pump.

The point is that oil is moved by force through an engine by a PD oil pump. It has nothing to do with gravity making it flow through a screen or making a ball dropped into a tube fall through the oil. That is just a method to measure viscosity, nothing else.

So in an engine, the same oil volume is forced by the pump through the oiling system to lubricate the engine, regardless of the oil viscosity. Oil is not forced to critical engine parts by gravity. A variable volume oil pump is still a PD oil pump.

 

[MolaKule]

My response to the needing thinner oils was not so much for bearing clearances, but because of the variable valve timing phasers or actuators that use very fine mesh screens to keep debris out of the works. And how much easier it was for a thinner fluid to flow through them, especially when the oil is very cold. GD&T was my life for many years.

I know what a plugged screen can do to VVT timing phasors as I was on a trip once and the VVT got confused in my 2003 PathFinder.

I would recommend an occasional cleaning using HPL's Engine Cleaner to keep the passageways and screens open:

https://www.advlubrication.com/products/engine-cleaner

 

[loneryder]

It is about fuel economy as well as what's adequate for an engine in typical use for its typical life.
We all know that really worn out engines will still run and move the metal down the road.
We also all know that 200K is a realistic life for a typical vehicle, since most drivers are reasonable with maintenance and not BITOG level OCD.
We further all know that there is nowhere in our country where you can go very fast for very long.
We can surmise that manufacturers recommend oil grades that will improve fuel economy while still providing for 200K durability as we typically use cars in the US.
Finally, we all know that if you track a car or highway tow then a thicker grade might be wise regardless of the typical use grade the manufacturer recommends.
For typical use I'm pretty sure that nobody is opposed to better fuel economy.

I really don't think auto manufacturers are shooting for 200k longevity. I think they just want to get you out of warranty.

 

[fdcg27]

I really don't think auto manufacturers are shooting for 200k longevity. I think they just want to get you out of warranty.

People have been saying that for years even as vehicles have gotten more durable, more reliable and more economical to run.
Industry standard durability is 150K and it isn't hard to get most vehicles past 200K.
I'd also doubt that the lenders who power the whole market would be very willing to finance anything for more than a couple of years if the expectation was that the collateral would lose almost all value at the expiration of the manufacture's warranty.

 

[Exhaustgases]

The point is that oil is moved by force through an engine by a PD oil pump. It has nothing to do with gravity making it flow through a screen or making a ball dropped into a tube fall through the oil. That is just a method to measure viscosity, nothing else.

So in an engine, the same oil volume is forced by the pump through the oiling system to lubricate the engine, regardless of the oil viscosity. Oil is not forced to critical engine parts by gravity. A variable volume oil pump is still a PD oil pump.

Oil viscosity is not tested in an engine. Maybe Molakule could help explain it?

 

[ZeeOSix]

Oil viscosity is not tested in an engine. Maybe Molakule could help explain it?

You need to do some study on how an engine's oiling system actually works (especially PD oil pumps), and the basics of Tribology to understand this discussion.

 

[kschachn]

You need to do some study on how an engine's oiling system actually works (especially PD oil pumps), and the basics of Tribology to understand this discussion.

This. A pointless discussion without that and it just goes from one gross misunderstanding to another.

 

[BMWTurboDzl]

Always thought it was only about fuel economy but with better manufacturing techniques and wanting better performance squeezed out of engines could it involve tighter tolerances as well?

Your thoughts?

Sort of

Engineers have been able to reduce the amount of internal friction which reduces heat and improve MPG. This reduction in heat allows for low viscosity oils.

 

[Exhaustgases]

It has been my line of study for the last 55 years or so.
The topic here was reasons for thinner oils. I just listed one item of concern.
And how thicker lube will not flow so great through a fine mesh screen.

 

[ZeeOSix]

It has been my line of study for the last 55 years or so.
The topic here was reasons for thinner oils. I just listed one item of concern.
And how thicker lube will not flow so great through a fine mesh screen.

Exactly what is the "concern" in an engine oiling system when you only know that a thicker oil flows slower through a paint filter screen under the effect of gravity?

If you've studied fluid dynamics for 55 years, and understand how an engine oiling system operates with a PD oil pump, then you'd know the volume flow will be the same going to all areas supplied by the pump, even if the oil a thicker, as long as the pump isn't in pressure relief.

As mentioned before, oil flowing through a screen due to gravity has absolutely nothing to do with how that same oil flows through an oiling system by force by the oil pump. It's like comparing aardvarks to bananas.

As mentioned by many in this thread, the reason for thinner oils is for more fuel economy to meet CAFE targets so the car manufacturers don't have to pay millions in penalties for not meeting the fuel mileage targets. There is no real "concern" about thicker oil working just fine in engines calling out a thin KV100 oil viscosity grade. The "W" (winter) rating of the oil is a whole other conversation. It's been pointed out many times that the same engines used in different countries call out a whole range of oil viscosity to use based on the ambient temperatures. Just how do they work and survive?

 

[OilUzer]

@Exhaustgases

What has been said is that a fixed volume of oil will flow or is forced to flow by the pump as long as oil meets or exceeds the W (winter) rating/requirement. As far as W rating, analogy would be like you can't force a fixed volume of water through a system if the water has been frozen.

Also oil being pumped or forced through a system by a PD pump is not analogous to oil flowing through a mesh by the force of gravity. That's because PD (Positive Displacement) pump will move a fixed volume of oil and maintain/force a constant flow rate ... whereas gravity doesn't.

If the oil was pumped somewhere up top and had to drip down and move through some tiny holes (by force of gravity) to lube some parts, that would be another story and the viscosity would matter I assume ... but the engines aren't designed like that, so I'm told.

 

[billt460]

The whole tighter clearance thing is utter nonsense. Why would Toyota spec their engines outside of the US to show everything from 20w-50 down to 0w-20 when 20w-50 is too thick for an engine "designed" for 20. It's the US's wonderful regulations.

Bingo. This has nothing to do with, "tighter clearances". Engines are made from the same materials as they always have been. These materials require the same hot running clearances as they always have. Cast iron, Aluminum, and steel expand and contract at the same rates as before.

They have to be able to operate in all types of temperature extremes, from well below zero, to high Summer desert heat. They wouldn't be able to without major issues, if the engines didn't have the proper hot running clearances, and were "tightened up". Pure hogwash.

This is all about fuel economy. Thinner oils provide less rotational resistance in an engine. Using them results in a very slight mileage increase, across hundreds of thousands of vehicles, in a fleet average over millions of miles driven.

And as you mentioned, they wouldn't spec different weight oils for the same engines, built with the same clearances, for different countries...... 4 letters explain all of this........ CAFE.

 

[MolaKule]

It has been my line of study for the last 55 years or so.
The topic here was reasons for thinner oils. I just listed one item of concern.
And how thicker lube will not flow so great through a fine mesh screen.

Oil flowing under gravity is irrelevant to the discussion here since engine oil is under pressure to create the proper flow rate. Here is a basic explanation of a pressurized oil system:

https://themechanicalengineering.com/types-of-lubrication-system/

As others have stated, lower viscosity oils are mostly for CAFE (Fleet Mileage) mpg targets.

Lower viscosity oils also reduce the amount of HP needed to move the engine oil under pressure, which, in turn, reduces oil temperature ever so slightly, but we're talking small fractions of gains here.

@Exhaustgases Oil viscosity is not tested in an engine.

I am not sure what this means. Oil viscosity verses temperature is tested in the Lab to predict the bulk oil viscosity in engines at various operating temperatures.

Now if your main concern is maximum oil viscosity verses VVT solenoid and phasor operation, then yes, there is a maximum oil viscosity specification. In both my old 5.3L Trailblazer engine and in my old 2003 PathFinder 3.5L engine (both of which I no longer own), the maximum viscosity spec was a grade of 10W30. This assumes those "last chance" screens and VVT control-valves are free of carbon.

Check your Owner's Manual for the Minimum and Maximum oil viscosity allowed.

Again, if you are concerned about keeping those VVT components clean, this product is highly recommended:

https://www.advlubrication.com/products/engine-cleaner

 

[ZeeOSix]

On top of regular OCIs with a good oil, If you want to keep those VVT filter screens clean, use a good oil filter that's on the high efficiency side, and one that doesn't tear media in service. Also, keep the engine RPM down until the oil warms up, which helps keep the filter out of bypass. Whatever gets past the main engine filter can end up in other secondarily screens/filters down stream.

 

[Bill7]

Always thought it was only about fuel economy but with better manufacturing techniques and wanting better performance squeezed out of engines could it involve tighter tolerances as well?

Your thoughts?

Fuel economy (about 1/10th of 1 MPG) so the automaker avoids more CAFE tax on the fleet of vehicles they sell.
The tighter engine clearances myth has been debunked as the same exact car/engine sold in Europe or Australia is spected at 5W-30 even 15W-40 in that region's owner's manual.

 

[OilUzer]

On top of regular OCIs with a good oil, If you want to keep those VVT filter screens clean, use a good oil filter that's on the high efficiency side, and one that doesn't tear media in service. Also, keep the engine RPM down until the oil warms up, which helps keep the filter out of bypass. Whatever gets past the main engine filter can end up in other secondarily screens/filters down stream.

At what typical temperatures can a typical filter go into the bypass mode? Are we talking about relatively very cold winter startup temps?
I assume it depends on the engine (e.g. pump), filter, oil W rating / viscosity, RPM, startup temperature , etc. No?
That's why I said typical. lol
Is there a generic answer or just be careful?

Do filter companies release a chart (viscosity, pressure, etc.)?
Pressure relief spec comes from the engine manufacturer I assume?

 

[hemioiler]

Sort of

Engineers have been able to reduce the amount of internal friction which reduces heat and improve MPG. This reduction in heat allows for low viscosity oils.

And on the other hand engineers are now running their engines hotter than ever. Speaking for my truck it can reach temps of 250+ degrees under load.

It's not because the hemi runs hot in and of itself, a lower thermostat + lower fan settings + more oil cooling can now mean the engine doesn't go past 200 degrees under the same load.

 

[ZeeOSix]

At what typical temperatures can a typical filter go into the bypass mode? Are we talking about relatively very cold winter startup temps?
I assume it depends on the engine (e.g. pump), filter, oil W rating / viscosity, RPM, startup temperature , etc. No?
That's why I said typical. lol
Is there a generic answer or just be careful?

Do filter companies release a chart (viscosity, pressure, etc.)?
Pressure relief spec comes from the engine manufacturer I assume?

An oil filter is going to go into bypass easier if the oil is cold and the engine RPM is higher. Lots of factors are involved; 1) The bypass valve setting, 2) Flow characteristics of the filter media, 3) Oil viscosity, 4) Engine RPM. There is no "generic" answer except the best thing to do is try to keep the engine RPM down until the oil warms up pretty good.

The filter designer (if they do it right) is going to determine the filter bypass valve setting based on: 1) The flow performance of the filter (dP vs flow), 2) The expected debris loading and dP increase over a recommended OCI, 3) The oil temp/viscosity and 4) The maximum expected pump output flow volume. A well designed and made oil filter should be able to withstand the bypass dP all day long without failing in any way.

 

[BMWTurboDzl]

And on the other hand engineers are now running their engines hotter than ever. Speaking for my truck it can reach temps of 250+ degrees under load.

It's not because the hemi runs hot in and of itself, a lower thermostat + lower fan settings + more oil cooling can now mean the engine doesn't go past 200 degrees under the same load.

It's getting complex that's for sure. Some engines have oil coolers with or without multiple water cooling circuits. As long as oil temps remain within spec thinner oils will get the job done.

 

[Corollaman]

It's all about fuel economy, plain and simple.