Will Thinner Oils Damage Your Engine?

[ZeeOSix]

How is the oil system itself accounted for? Flow rates, for example. What if anything can account for the finish in oil passages with sand cast? Are they just over sized or machined? I would guess they are sized for a viscosity range. Do the oil holes for rods or mains act as orifices, that is, is cavitation a consideration?

A positive displacement oil pump will overcome things like the slight flow resistance that rough sand cast oil passages (etc) can cause. Yes, all holes act as a flow orifice (ie, flow regulator) and need to be sized to ensure proper oil flow volume to the parts needing lubrication - lack of oil supply can obviously be very detrimental. The whole oiling system design is pretty involved.

Some people claim (without hard evidence) that the ticking in the Coyote (Ford calls it the 'typewriter tick' in their bulletin - and not all Coyotes do it) might be caused by journal bearing oil cavitation. But all the info on bearing cavitation points to it not being cavitation. Personally, I think it's a mechanical tick that is highly dependent on the friction level of the oil because when people add even 150cc (~1/6 qt) of anti-friction modifier (like LiquiMoly Ceratec) to 10 qts of oil the ticking disappears almost instantly.

 

[ZeeOSix]

Z's answer is essentially correct on the protection but lets explain it with an analogous example as people may not be able to relate to it.

Lets say you have an engine designed for 50 HP @ 100RPM with a bng clearance of .004" and a lube system giving 50gpm@50PSI .

You do the 'secret stuff" ( metallurgy, heat treatment, poisons wedge and all that) and determine it takes 20 MOFT units ( yes that's a made up measurement for illustration purposes)

That's the design spec and all that's hard built into the engine and cant be changed without physical modification.

So, a 20 oil gives 23 units, a 30 gives 27 and a 50 gives say 32 units of MOFT.

The OEM decides the baseline spec will be 30 ( picks mid range based on his design performance standards which is ALL he is married to)

So within tolerance you can change that with varying levels of MOFT change but within acceptable limits so you are OK (ish)

Now you operate it differently ( lets say now you are getting 70 hp @ 175 RPM) but didn't change everything else

You may find the original recommendations inadequate or whatever you change to isn't all you need.

That's why this is not a direct linear answer because multiple things go into what the necessary MOFT has to be and multiple factors affect what has to be changed to maintain it the further you get from the OEM design range.

Some of this is IP so you have to guess or experiment.

Agree that there are many factors involved. MOFT units are in microns BTW. HP level wont have much effect on MOFT at higher RPM because MOFT naturally builds with increased RPM, but it also results in increased oil temperature which reduces viscosity and MOFT. What's dangeraous IMO is if an engine is lugged at low RPM with high throttle opening, which ultimately could cause less MOFT in the journal bearings. So thinner oil users (especially towers) should keep that in mind and not live at too low of RPM with the engine under high loads. Probably why some engine manufacturers recommend going up a grade for heavy use situations like towing, etc. Of course, employing an effective oil cooling system allows for a thinner oil to be used. It's all about real time viscosity between parts, relative speed between parts and the resulting MOFT to keep parts from contacting and wearing.

 

[RDY4WAR]

Should we also consider the conditions in which Sequence IIIG (ASTM D7320) and Sequence IIIH (ASTM D8111) are ran? A total of 90 hours run time broken up into 4x 20 hour sessions and 1x 10 hour session. Run at 3900 rpm with coolant temp at 239*F (115*C) and oil temp at 304*F (151*C) under a load of 184 lb/ft (250 n/m).

Considering that, I think most of your daily commuters cruising along at 65 mph on the highway with little load, 220*F oil temps, and 2000 rpm will be just fine.

 

[ABN_CBT_ENGR]

How is the oil system itself accounted for? Flow rates, for example. What if anything can account for the finish in oil passages with sand cast? Are they just over sized or machined? I would guess they are sized for a viscosity range. Do the oil holes for rods or mains act as orifices, that is, is cavitation a consideration?

In the most basic of systems (fixed displacement PD and tied to RPM) and in layman’s English, here is how this works (maybe sacrificing a wee bit of technical accuracy but we are not measuring nanometers)

Liquids do compress and factors such as surface tension, viscosity, temp, Sg etc determine how hard they get and the EHD “wedge” has “x” volume on the front and increases in velocity on the way out.

During that cycle you have a minimum of 3 laminar flows combatting each other.

The flow on the smaller surface with the smaller surface feet per minute contact.

The flow on the outer surface with a larger SFPM contact

The buffer layer in the middle which acts like a shock absorber and is the primary maintainer of the MOFT. ( It is usually absorbing the heat generated by the other two and cooling it to a degree)

All of that is a calculated value in terms of volume and velocity the pump has to provide in all operating envelopes to maintain the proper MOFT.

My experiences with passages in machines ( with the exclusion of high speed precision spindles and similar) is to regard them as rough pipe ( in terms of flow friction) and size the pump accordingly.

“Sized accordingly” means whatever the OEM says it means so be careful there.

This is why when you have wear (dimensions open),, significantly change heat, RPM’s, Load or viscosity, pressure changes ( and flow along with it to a degree)

I can’t speak to automotive application but the oil holes and passages do act like orifices ( fixed flow regulators) to add a little bit of back pressure right before it enters the tolerance chamber ( like releasing spring tension at the moment of truth but in a metered controlled way to avoid whirl or potential cavitation)

Cavitation in an oil system is very unlikely except in the bearings where various wears or other misalignments can create zones where pressure aberrations can occur.

I know I add 100% ish and size the pilot relief accordingly and I’m sure automotive engineers do something similar to cover all reasonable operating envelopes.

Now to the ‘mysterious magically changing MOFT”

In true EHD there is no metal to metal contact ( we need to remove ramp up and ramp down thermal expansion and all those things because there will be some contact in those periods- in true steady state is where everything lives after that) but nothing is perfect and neither is tribology so there is some contact.

If all things previously discussed stay even (very big if) then changing a viscosity alone (no other property) won’t affect anything but the parasitic load it takes to pump it ( this is assuming the viscosity is capable of generating the MOFT necessary with the lubrication pump and system set up- but that’s not a property of the oil)

Now come the special cases and exceptions- (too many to list but here are some)

If there is a multi-grade oil that meets the lab spec but your actual running condition is different- you may have a problem

Engine now has 175k miles and tolerances are opened- you may have the flow but not the back pressure in the journals so can’t achieve or hold MOFT in all conditions.

To sum it up

In engine “X”- thinner ( or thicker) oils because they are thicker or thinner will have no effect on anything except consuming the energy required to pump them PROVIDED the viscosity selected is within whatever requirements the engine is built and used for. ( that puts the “magnum onus” on the person doing the selecting to do the proper up front engineering- not on the name on the bottle)

To not do the proper up front engineering to decide the optimum viscosity for your specific application is playing roulette- best of luck.

The question as stated in the OP is both yes and no depending on everything else and coming to the proper conclusion as to viscosity is or isn’t “bad” is an engineering exercise not a parliamentary or democratic one.

 

[ABN_CBT_ENGR]

MOFT units are in microns BTW.

I was using an analogy to describe an effect to the non engineering readers- not giving a measurement

 

[xyxptlx]

Yes, all holes act as a flow orifice (ie, flow regulator) and need to be sized to ensure proper oil flow volume to the parts needing lubrication

I know I add 100% ish and size the pilot relief accordingly and I’m sure automotive engineers do something similar to cover all reasonable operating envelopes.

Thank you I hadn’t considered the effect of positive displacement.

Would a radius on the oil holes work to enhance oil flow or does it end up changing the “head” pressure, if you will.

I’ve read that a little bit of radius on the pump outflow can enhance flow, albeit the cost of incremental power?

 

[MaDMaXX]

A positive displacement oil pump will overcome things like the slight flow resistance that rough sand cast oil passages (etc) can cause. Yes, all holes act as a flow orifice (ie, flow regulator) and need to be sized to ensure proper oil flow volume to the parts needing lubrication - lack of oil supply can obviously be very detrimental. The whole oiling system design is pretty involved.

Some people claim (without hard evidence) that the ticking in the Coyote (Ford calls it the 'typewriter tick' in their bulletin - and not all Coyotes do it) might be caused by journal bearing oil cavitation. But all the info on bearing cavitation points to it not being cavitation. Personally, I think it's a mechanical tick that is highly dependent on the friction level of the oil because when people add even 150cc (~1/6 qt) of anti-friction modifier (like LiquiMoly Ceratec) to 10 qts of oil the ticking disappears almost instantly.

Thankyou for addressing the Coyote in the room, it's the main reason i'm in this thread

So, if i'm understand/remembering the role of an antifriction modifier, it's actually to introduce some friction?

 

[ABN_CBT_ENGR]

Thank you I hadn’t considered the effect of positive displacement.

Would a radius on the oil holes work to enhance oil flow or does it end up changing the “head” pressure, if you will.

I’ve read that a little bit of radius on the pump outflow can enhance flow, albeit the cost of incremental power?

In the CFD world, that’s usually referred to a “bellmouth orifice” and it’s almost always a 60° chamfer but can have any number of profiles.

What it does is allow for a little expansion and increase in surface area which will serve to reduce fluid friction a bit ( a lot of this depends on the actual tolerance of the area to be lubricated and flow volume so it’s difficult to generalize)

It “can” have a reduction in shearing forces (that’s a different science altogether)

All things being equal, it would not have any effect on pressure except on designs where it is made into an inverted type nozzle/injector in a bowl but I have personally never seen that in a lubrication system application.

Any power loss from something like this would be in nano-joules so I wouldn’t worry about it

 

[blingo]

With the subtext I must be missing out on parts of the analogies. Societies demanding street fuel efficiency (and not only enforcing that by raising taxation on fuels) doesn't look the same to me as parliament and democracy coming over to the drawing boards and specifying thinner and thinner lubricants for mills and paper machines.
On firmer ground: More or less the right amount of that demand seems to be trickling down as 0W-20, 0W-16,.. into these ICE oil pans and dry sumps of Toyota so far. And these passenger car companies are already much about leaving the building of these internal combustion engines.
So what about an addition of some passive-aggressive heavy duty whataboutism? Would for example something like an FA-4 as it is growing on me better be understood as something the transportation should beat off with all its might before it's too late? Before it might be established and proven and saving money and fuel and sparing CO2? I see, time is running out and Joules are beeing summed up, but I'm not too convinced yet.

Some analogies may have been flawed before reading. A broader focus on efficieny to be had from engineering in general will be due. For Engineering Explained this could at least become easier to picturize – more monogrades and less transiency off the road.

 

[ABN_CBT_ENGR]

With the subtext I must be missing out on parts of the analogies. Societies demanding street fuel efficiency (and not only enforcing that by raising taxation on fuels) doesn't look the same to me as parliament and democracy coming over to the drawing boards and specifying thinner and thinner lubricants for mills and paper machines.
On firmer ground: More or less the right amount of that demand seems to be trickling down as 0W-20, 0W-16,.. into these ICE oil pans and dry sumps of Toyota so far. And these passenger car companies are already much about leaving the building of these internal combustion engines.
So what about an addition of some passive-aggressive heavy duty whataboutism? Would for example something like an FA-4 as it is growing on me better be understood as something the transportation should beat off with all its might before it's too late? Before it might be established and proven and saving money and fuel and sparing CO2? I see, time is running out and Joules are beeing summed up, but I'm not too convinced yet.

Some analogies may have been flawed before reading. A broader focus on efficieny to be had from engineering in general will be due. For Engineering Explained this could at least become easier to picturize – more monogrades and less transiency off the road.

You must be missing out on about everything it seems and from your comments not much of an overall understanding of the subjects in general so let me help you better grasp the key points

CAFE applies only to automotive, not industry and its law and politically driven- not mandated by an engineering requirement

It wouldn't apply to the FA-4 either as in most cases the military is exempt

Industry generally uses single grade ISO lubricants, not multi grades so its a whole different thing.

It has nothing to do with saving money- its about "green energy" and the things attached to it. ( a scam disguised as something good for the environment)

 

[OilReport99]

Societies demanding

That's the laugh of the day

 

[ZeeOSix]

Thankyou for addressing the Coyote in the room, it's the main reason i'm in this thread

So, if i'm understand/remembering the role of an antifriction modifier, it's actually to introduce some friction?

The anti-friction modifier reduces friction between moving parts. My theory is that the big ends of the connecting rods (depending on the side clearance on each individual engine) are moving side to side and can impact the side of the crank journal and make a ticking noise. If the friction is reduced some, the rod ends many not get triggered to move side to side so much as the engine rotates. Just a theory, no hard proof to verify that.

The random Coyote ticking at idle sounds just like this - rod big ends slapping on the side of the crank journal.

 

[blingo]

Thank you, gentlemen. I can really leave it at that.
"Overall understanding" beeing my laugh of the day ;-)

 

[wtd]

The anti-friction modifier reduces friction between moving parts. My theory is that the big ends of the connecting rods (depending on the side clearance on each individual engine) are moving side to side and can impact the side of the crank journal and make a ticking noise. If the friction is reduced some, the rod ends many not get triggered to move side to side so much as the engine rotates. Just a theory, no hard proof to verify that.

The random Coyote ticking at idle sounds just like this - rod big ends slapping on the side of the crank journal.

We have three Coyote 5.0's in the family and none of them have a tick. My 14 Mustang GT has 32.000 miles on it. My fiancee's 17 F150 has 23,000 miles, and her son's 14 F150 has 195,000 miles on it. It is currently in the shop for repairs because of a possible timing issue but no ticks. We must have gotten lucky so far.

 

[PimTac]

Just because a thinner oil is specified for the engine doesn't mean it's giving the same level of wear protection as a thicker oil. The most basic result of tribology research shows that MOFT is a direct function of the oil viscosity, and MOFT increases with viscosity. In non-CAFE countries where the same US manufactured engines are used, they typically spec a little thicker oil and/or show them as optional in the owner's manual.

CAFE is the main driver of thinner and thinner motor oils specified for use in the USA.

Wear protection may be the precursor to engine damage or maybe not.

My current vehicle is the first one to run 0w20 and according to my non-scientific ears, it runs so quiet I have to look at the tachometer to make sure it’s running. Quiet running to me tells me that the oil is doing the job.

 

[ZeeOSix]

Wear protection may be the precursor to engine damage or maybe not.

You mean low or lack of wear protection? If the wear somehow kicks off in a drastic way and it causes a cascade effect, then real damage could occur.

Sure, an engine can wear quite a bit and still "run good" as reprieved from behind the wheel and not technically be "damaged". Rings and bearings seem to be more prone to wear from lack of MOFT, so signs of those wearing would be lower compression and increased oil usage sooner than expected, and maybe lower oil pressure and/or bottom end noises. But an engine has to be pretty worn to exhibit those signs.

 

[MaDMaXX]

Alright, so let's look at a theoretical example here.

Coyote engine, not ticking, calls for 5w20, known to shear a lot(?) what conforming oil would be strongest against the shearing? and is a strong shear strength oil a good idea for it?

 

[blingo]

5W-20 already is one solid approach, 5W-30 would have a tendency for the worse (and 10W-30 probably be unnecessary then, but I'm not into Coyotes). But 5W-20 oils may be more of a mixed bag than 0W-20 oils, so the solidity in approach in theory becomes uncertain here in practice.

The engine usually is big enough to not have one size, grade, concept or particular lubricant fit all points of lubrication (or points hurting lubrication). A 5W-20 mostly free of VM (perhaps lower in KV100 while higher in HTHS when standing in front of the shelves) may miss out on benefits from VM that are just no popular conversation piece around here: https://360.lubrizol.com/2020/A-Study-in-Sand-Part-3
This whole thread is very much about missing out on overall grasping. More like finding one point of lubrication in one engine that would be fine with the one lubricant, understanding and size 42. Fortunately much of it ain't of much importance. But the Coyote may vary, I wouldn't know...

 

[Zaedock]

We have three Coyote 5.0's in the family and none of them have a tick. My 14 Mustang GT has 32.000 miles on it. My fiancee's 17 F150 has 23,000 miles, and her son's 14 F150 has 195,000 miles on it. It is currently in the shop for repairs because of a possible timing issue but no ticks. We must have gotten lucky so far.

My '12 F150 5.0L also is quiet (see below*). I saw something regarding this engine shearing oil, but I have never experienced or heard of it.

There was a TSB however, for a periodic knocking sound that we had to deal with. The dealer could never hear it and said "it sounds just like the rest of the trucks on the lot". My wife then recorded it and went into full Puerto Rican mode on them. Needless to say, they had the whole shop listen to it the next morning and heard the knocking sound. The culprit - cylinder 3 was not round. It was a manufacturing defect. When the rings spun to a certain position, you could clearly hear it. The dealer ordered a new updated engine from Ford and I had a free F150 loaner until it was ready. That was at approx. 24,000 miles and I only have 70,000 miles on her. The new engine has been flawless and quiet.

 

[aquariuscsm]

I remember back in 2012 I kept hearing the new Ford 5.0 engines would "drop a piston" requiring engine replacement. What exactly did that mean?