Is more really better?

[TrainingPolicy]

Recently, I keep reading more and more threads and people are saying that "since the car takes 8 quarts of oil, I run it longer" or how ever many quarts it takes, if it takes more than 5 quarts. Yet, I never hear people saying that if a car takes less than 5 quarts they run it shorter. For example a 2005 corolla take 4 quarts of oil, and I know plenty other cars are similar as well, yet the OCI is never decreased simply due to the oil capacity. Is this idea based in any science or is it simply, ‘it has more so I can use it longer' mentality? TIA!

 

[Kamele0N]

Oil capacity corelates also with how thermaly "loaded" one engine is....

Look on amount of oil also as it would be its cooling media...

Lets say that you have the same engine block with different outputs...

1.8 N/A....it holds 4quarts of oil...

1.8 N/A with different camshafts and therefore higher HP output....4.5 quarts

1.8 TFSi....with even more HP.... 5.5 quarts of oil + an oil cooler

Etc...

 

[4WD]

Higher capacity can offset fuel dilution …
… my 2010 5.3L was not direct injection (DI) …6 quarts … my 2018 5.3L is DI …8 quarts

 

[daves87rs]

Originally Posted by Kamele0N
Oil capacity corelates also with how thermaly "loaded" one engine is....

Look on amount of oil also as it would be its cooling media...

Lets say that you have the same engine block with different outputs...

1.8 N/A....it holds 4quarts of oil...

1.8 N/A with different camshafts and therefore higher HP output....4.5 quarts

1.8 TFSi....with even more HP.... 5.5 quarts of oil + an oil cooler

Etc...





Yep, depends on many factors......

 

[ZeeOSix]

The recommended oil change interval the engineers put in the owner's manual should reflect the sump capacity to some degree.

 

[ABN_CBT_ENGR]

Originally Posted by TrainingPolicy
yet the OCI is never decreased simply due to the oil capacity. Is this idea based in any science or is it simply, ‘it has more so I can use it longer' mentality? TIA!


The correct answer is the majority of people making these statements are basically using the "3 blind men describing an elephant" method of anecdotal engineering.

Sump engineering ( wet or dry) is a science unto itself and those outside of machine design probably don't even know it exists. (I know I didn't when I started and I was brought up to believe many of the things currently stated about sumps and levels and had to change my whole way of evaluating them)

In a very short tutorial ( and hardly comprehensive) the sump level ( dipstick) is DECOUPLED from the lubrication level ( defined as the lubrication necessary to lubricate the machine)- that's a distinction with a difference as will be seen.

So you start with the volume of "active lubrication" with a thermal load and come up with a cooling cycle- that's your baseline.

Then consider the delivery system ( pump, splash etc)

That gives you a basic volume then you need to cool it ( determines the physical properties of the sump as below the thermal zone, thinner metal for thermal transfer, air flow etc)- You really cant overfill a sump that is decoupled from the active or thermal zone of the machine. This is why some gearboxes and couplings have different fill levels and volumes for different orientations.

Then you have the pick ups and levels relative to tilt, orientation, sloshing and so forth.

That's basically the universal fundamental method then everything beyond that goes application specific and that's a whole different level and type of considerations and often has a lot of T&E built in.

On the change part- the forces acting against the oil determine its service life and depending on what specific quality of the oil in question- volume can play a part in the interval and in some situations it doesn't.

So there is a science to it but its not an absolute and it has a lot of things to consider.

 

[Mr Nice]

More oil = longer oil change intervals.

 

[eljefino]

"They" say to change oil after a certain amount of fuel has run through. They use this for oil-life-monitors. More cold starts, more idling, more city traffic means more fuel burned per mile, and a shorter OCI.

A corolla is good on gas and burns less fuel, so it fatigues its oil more slowly. There's less of it, so we see a normal-ish change interval.

(The flip argument is a tiny engine is wound up more of the time, and would shear it down faster.)

I also think some engineers know the American market, and how Jiffy Lube gives everyone 5 quarts for the normal price, and oversizes their sump capacities to take those 5 quarts as a buffer against running long, or running low.

 

[HangFire]

If it's a wet sump engine (vast majority of automotive engines), it's not entirely decoupled from the engine lubrication, is it?

There is a general correlation between factory vehicles with very long OCI's, and the size of their sumps. But there are also similar correlations between turbo engines and their sump size, and performance engines, except a few where there is not.

My 1.8L Corolla takes half a quart more oil than my 3.9L V6 Dakota. Make of that what you will.

 

[supton]

I sorta do that. I have vehicles with 4, 5 and 8 quart sumps. The 8 quart sump is lightly loaded--heavy truck that is barely used and has an oil cooler. The 5 quart vehicle sees "typical" usage and gets 5k in winter, 10k in summer. The 4 quart sump one has no engine oil cooler and has to live under my right foot--if it wasn't for it using a quart over 3 or so k I'd probably change all the sooner.

IMO the OEM's tend to take this all into account. A 3 or 4 quart sump was deemed sufficient for typical by the OEM for whatever duration they wrote down. We at BITOG like to overthink things, and I enjoy my little world of FUD. But you have to admit, the smaller the sump the cheaper it is to change.

 

[ABN_CBT_ENGR]

Originally Posted by HangFire
If it's a wet sump engine (vast majority of automotive engines), it's not entirely decoupled from the engine lubrication, is it?

There is a general correlation between factory vehicles with very long OCI's, and the size of their sumps.


No its not but it is ( let me explain because its literally up to the individual design team and what they considered important and what they didn't)

X+Y= 7- At this level there is an infinite ability to relatively define X & Y- that's how sump calcs go. This is basically the same info in the ML-1 &2 sump training and this subject comes up often.

At any level there is a "correlation" between volume and lifecycle of a lubricant but its hard to define based on that because each variable ( need to dissipate heat, particulate contamination, chemical contamination, additive consumption and tons more) has a different effect and impact on the overall lifecycle relative to total volume available. That's not even attempting to capture end use specifics like the way you personally use the machine.

(Particularly in an ICE rather than in most industrial equipment which run usually steady state)

The designer cannot possibly capture them all or investigate every possible scenario- the only "standard" is the heat removed from the various regimes so that's what the baseline calculation is based on.

They everything else is best guessed with a good margin of error. Theres also input from lube manufacturers and inputs from various studies and all that.

Theres a lot of room built in for error, expansion and other things.

 

[buster]

Ted Kublin (Tooslick), who was one of the most knowledgeable people on this site at one time came up with this formula.

OCI = (C*)(ave mpg)(sump in qts)(cubic inches/Hp)

"Where C* is a constant which was derived by looking at oil analysis data I've accumulated over the last 10 years. For Amsoil I use a C* of 120, which generates drain intervals of approx 7500 miles for a turbo or motorcycle, up to 15k-20k for a low power density engine driven easily on the highway. If you have an application where you are dirt or soot limited, you can't use this formula and get a good estimation of oil life.

You CANNOT use the TBN times ten as a substitute for this C* value. The rate of TBN depletion varies significantly depending on the quality of basestock and additive chemistry. In addition, TBN depletion is non-linear, as you have seen from the 3MP tests. In other words, a 6 TBN oil will not last 50% as long as a 12 TBN synthetic. In actual practice, it might only last 25%-33% as long.

I don't have as much data on other oils as I do with Amsoil in deriving additional C* values. For Mobil 1 I suggested using a C* of 80, based on the limited data I've seen on this site. For an average quality petroleum lube, I think a C* of 40 is reasonable. The implication of using these various C* values is easy to see ....

Please feel free to contact me off-line if you have any other questions about this OCI formula. BTW, I've made my living as a propulsion engineer for the past twenty years - the Amsoil stuff is something I do on the side."

 

[RDY4WAR]

I feel like the sump capacity does have an impact on service life, but not as much as the engine itself. Take 2 engines that are exactly the same except one has a 4 quart sump and the other has a 6 quart sump. The 6 quart engine can spread the same fuel dilution, water dilution, combustion by-products, soot, etc... across more oil (50% more) and therefore should result in slower TBN loss. The higher sump capacity would also mean more cooling which would slow oxidation. Though I've never done an A-B-A test of this myself, I surmise that a larger sump capacity, with all else equal, would result in a longer service life.

 

[Revving2Redline]

I follow the MM on my Honda. Granted I know this car up and down and have had various samples taken to know where the end of the oil fill is at. I have noticed that my fuel quality, air and oil filtration and willingness to check the oil level every month and top off if needed has contributed to its longevity.
As I get closer to buying a brand new civic which has a small oil sump I will consider many options to keep oil in safe operating. I'm not too worried about fuel dilution with non ethanol fuel and highway driving. Will run a 3.0 or higher hths oil and possibly a small oil cooler from GReddy or Mishimoto. Think the thinnest I'll go is redline 0w20 or blend M1 0w30 / Redline 0w30.

 

[CT8]

It depends.

 

[CharBaby]

I follow the MM on my Honda.

What % do you take your OCIs down to before changing?

 

[ABN_CBT_ENGR]

Originally Posted by RDY4WAR
I feel like the sump capacity does have an impact on service life, but not as much as the engine itself. I surmise that a larger sump capacity, with all else equal, would result in a longer service life.


That's really the best it can be broken down to and you really see it when you deal with sumpless designs.

The key thing to remember when calculating a lubricant service life is that averages are fine for spreadsheets, discussion forums and statistics but when you have a machine that must have certain qualities of a lubricant where the degradation of those qualities initiates additional heat and/or other damaging factors the life becomes asymmetric and hyperbolic for the fluid life.

Fluid life ( in terms of requirements for an application) is not a linear degradation over a timeline based on a rate- they are dynamic and highly randomized because as each part of the lubricant package degrades ( assuming machine remains mechanically a constant) then the outputs change which then affect other parts of the lubricant.

You don't see this probably as much on an ICE but that's because most cars do not have industrial grade continuous monitoring with vibration, thermal, UT capabilities trended on programs.

When you compare oil sample rates to those properties they will really reveal themselves as to how they are all interdependent and affect many things- which in turn affect many others like a cascade effect.

 

[4WD]

Case in point … we run large fixed CAT engines. OEM gives the maintenance guys the hours on an OCI and the (active) sample frequency. But a good showing on an UOA is not a ticket to run the oil longer like folks on this site might use it.

The numbers were developed while testing and after that empirical data is checklist stuff.

 

[ABN_CBT_ENGR]

Originally Posted by 4WD
Case in point … we run large fixed CAT engines. OEM gives the maintenance guys the hours on an OCI and the (active) sample frequency. But a good showing on an UOA is not a ticket to run the oil longer like folks on this site might use it.

The numbers were developed while testing and after that empirical data is checklist stuff.


Absolutely and depending on both the oil and sample- the lab may not be testing all of the parameters that directly affect wear ( but will show up in PdM)

and some additives simply do not have adequate and accurate testing methods yet.

I see it all the time, people get the basic ( cheapest or free) test and base all things on that when often that level test alone is almost worthless unless the end goal is to build a trend line.

That's the difference between a properly engineered lubrication/equipment management plan and those who build one from Google and solely based on marketing claims and YouTube.

Then they come to us wanting it solved and wee have to educate them.

Glad you brought that critical point up.

 

[Fattylocks]

Is more really better?

Of course it is. If a little is good, more is better.