Optimal kinematic viscosity for mimimal wear?

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Originally Posted By: BuickGN
Where's the article that stated that increasing the HTHS up to something crazy like 11 or 16 reduced wear with each increase...

I'm sure that such a substance would run just beautifully in an Accord or Camry...

Originally Posted By: BuickGN
And come on guys with this whole thing about bearings and cylinders hanging on till the oil pressure arrives. Oil pressure isn't more than half a second behind the first revolution of the crank.

Is it? Always? Well, if you assume that everything is optimum, and you have an engine that idles at ~800 rpm, and it's of course starting from zero rpms, and using your 1/2 sec assumption, then by my rough calculations, the engine will experience a couple dozen or so revolutions without oil pressure. Not disastrous, but certainly enough to raise the specter of wear happening on start. Particularly when considered on a cumulative basis.

I would neither over-minimizing, nor overdramatize, this phenomenon. Again, why would the Toyota engineers felt it necessary to have the hybrids pre-oil themselves on start? Why are pre-oilers for sale?
 
Race engine not wear out they break; street simply wear out.

The notion that 20 wt oils is something new is simply not true.
I'd argue that they have been in the sumps of a high percentage of cars all along although unwittingly. It is only recently that typical dino 5W-30 oils have been able to stay in grade for even 3000 miles.
I remember reading a Consumers Report on multi-grade motor oils back in the 80's and they all sheared to some extent, 2/3rd out of grade and a few down to a 10 wt oil all after only 3000 miles.

A mfr specifying a 20 wt oil that they know will stay in grade seems a pretty conservative stance to me.

As far as Bimmers and other European engines needing 40, 50 or 60 wt oils simply isn't true for cars only driven on the street vs track day events. I'm running a 5W-20 syn in mine because in my application and climate the oil temps rarely hit 100C let alone exceed it. The standard dealer fill is Castrol BMW spec' 5W-30 for most BMW's up here.
 
Originally Posted By: CATERHAM


As far as Bimmers and other European engines needing 40, 50 or 60 wt oils simply isn't true for cars only driven on the street vs track day events. I'm running a 5W-20 syn in mine because in my application and climate the oil temps rarely hit 100C let alone exceed it. The standard dealer fill is Castrol BMW spec' 5W-30 for most BMW's up here.


Race engies do wear out without breaking sometimes. This has happened several times to me with a thin 30wt in place of the 20w-50.

This is an example of what I'm talking about. So it's ok to go down in weight based on temperatures and driving style but if anyone suggests going up a weight due to a hot climate/aggressive driving, they're told the manufacturer knows best and not to do it. This isn't so much aimed at you but most of the thin crowd.
 
Originally Posted By: ekpolk
Originally Posted By: BuickGN
Where's the article that stated that increasing the HTHS up to something crazy like 11 or 16 reduced wear with each increase...

I'm sure that such a substance would run just beautifully in an Accord or Camry...

Originally Posted By: BuickGN
And come on guys with this whole thing about bearings and cylinders hanging on till the oil pressure arrives. Oil pressure isn't more than half a second behind the first revolution of the crank.

Is it? Always? Well, if you assume that everything is optimum, and you have an engine that idles at ~800 rpm, and it's of course starting from zero rpms, and using your 1/2 sec assumption, then by my rough calculations, the engine will experience a couple dozen or so revolutions without oil pressure. Not disastrous, but certainly enough to raise the specter of wear happening on start. Particularly when considered on a cumulative basis.

I would neither over-minimizing, nor overdramatize, this phenomenon. Again, why would the Toyota engineers felt it necessary to have the hybrids pre-oil themselves on start? Why are pre-oilers for sale?


I'm not arguing about how practical an oil with an HTHS of 16 would be but it was interesting to note that wear with everything at full temp does go down as HTHS increase. This was also proven by GM with a more sensible HTHS and a very signifigant reduction in bearing wear.

Hybrids start and stop the engine 100 times as often as a normal car. The insignifigant amout of wear that we see during startup all of a sudden becomes signifigant. It could also be for some sort of emissions/economy reason too. Engines aren't too efficient in any way at 400rpm.

Why are people so worried about that extra milisecond to pressure yet not worried about the absolute best ADBV filter available? I'll say this again, you can't tell a difference in time to full pressure between a 30wt and a 50wt so long as it's acceptable in your climate. I would rather have a thicker cushion of oil on the bearings before pressure arrives than a thin one. Same goes for the cylinders. And what's most likely to partially run off overnight, the thin or the thick oil? That last point is really moot, I've never torn an engine apart that didn't have a nice coating of oil on the cylinders.
 
Can I pile in on the beat down? j/k
grin2.gif


Lots of valid stuff ..but

Quote:
Lets just clarify that the start up wear


Start up wear, in the context of "90% of all" is defined as 20 minutes ..where virtually all wear occurs. I'm sure it's on a curve that is at its highest at initial firing, but it's not limited at all from the time you hit the key until full lubrication is established. That wear curve to full warm up is how SAE defines "start up". I'll also agree that it's a cold engine scenario due to additive reaction inhibition ..but I also think expansion characteristics of some parts play a decent role too. I think I've seen some mentions of corrosive aspects that you speak of, but I didn't get the impression that they were the dominant player in total start up wear.

Quote:
Then, lets answer the original question. The optimal wear is achieved with heavier rather than thin oil. The heavier oil will separate moving parts better than thin oil under pressure conditions. The reason thin oils are utilized successfully, is that ZDDP and other additives prevent excessive wear under full metal contact seen in thin oil under pressure (valve train). Thin oils provide better fuel efficiency as they decrease friction at the ring/cylinder interface at the expense of minor increase of friction in valve train and a potentially higher wear under heavy load and high oil temp.


The particulars here I don't have too much argument with, but it assumes that some "limits" are ever challenged. So, while higher visc will indeed separate parts better ..who's to say that half of that isn't enough? This is the flaw in that reasoning.

Quote:
Notice that 18 wheelers use 15W40 rather than 0W20.


This comes from the same machinery lubrication authoritative sources that also say "thicker oil produces less wear". What's taken out of context is the commercial machinery (be it whatever it is) is designed for it's near full time duty cycle at maximum load. You don't buy them to loaf along @ 30% utilization. Automotive engines are probably well below that on average.

I'd say it's the same for anything that has a higher specific output and/or power density.
 
Originally Posted By: CATERHAM
Race engine not wear out they break; street simply wear out.

The notion that 20 wt oils is something new is simply not true.
I'd argue that they have been in the sumps of a high percentage of cars all along although unwittingly. It is only recently that typical dino 5W-30 oils have been able to stay in grade for even 3000 miles.
I remember reading a Consumers Report on multi-grade motor oils back in the 80's and they all sheared to some extent, 2/3rd out of grade and a few down to a 10 wt oil all after only 3000 miles.

A mfr specifying a 20 wt oil that they know will stay in grade seems a pretty conservative stance to me.

As far as Bimmers and other European engines needing 40, 50 or 60 wt oils simply isn't true for cars only driven on the street vs track day events. I'm running a 5W-20 syn in mine because in my application and climate the oil temps rarely hit 100C let alone exceed it. The standard dealer fill is Castrol BMW spec' 5W-30 for most BMW's up here.


Cate Rhan or Cater Ham (I don't know which),

I thought you asked a question and wanted to hear an answer. Apparently that is not a case as you have your own dogmas and you are not interested in answers backed by science.

I will remind you that you asked about optimal viscosity for wear protection, yet you really wanted to hear that the synth 20 oil you use is the best thing under sun. Yes. it may be the best oil solution for your application, but it is not the optimal viscosity to prevent wear under all circumstances.

Clearly I wasted my time.
 
Originally Posted By: Gary Allan
I think I've seen some mentions of corrosive aspects that you speak of, but I didn't get the impression that they were the dominant player in total start up wear.


I've seen some good evidence for that in SAE papers by Japanese authors where they used radiotracer technique to measure wear at different temps with different amounts of sulfur in fuel. Look at the figure 20 on page 9 here: http://hosting.dynamis.net/littlerocket/MMCAllAluminumCylinderBlock(2ZZ-GE).pdf

The authors write:
"Fig.20 shows the results of ring wear measurements by
varying the inlet cooling temperature. The lower the
coolant temperature, the greater the wear. This tendency
become more pronounced when the coolant temperature
is 40 degree celsius and below. Furthermore, even in the
case of high-sulfur fuel, ring wear is small when the water
temperature is 80 degree celsius and above. As can be
seen in Fig.17, change in coolant temperature manifests
the change in wear rather quickly.
This mechanism is as follows:
• Acids in the bore increase when coolant temperature
is low.
• The acids eliminate oil film between the bore and
piston rings.
• Abrasive wear between the bore and piston rings
increase."

Now, this deals with ring/cylinder liner wear mostly and it's less applicable to other parts of engine. Yet, it's very conclusive.

Ironically, the same BITOG members who the most vocal in the silly 5W30 vs 5W20 discourse close their eyes to factors that are more important than the trivial viscosity difference of 8+ vs 9 cst at 100C.
 
Originally Posted By: friendly_jacek
. . .
I will remind you that you asked about optimal viscosity for wear protection, yet you really wanted to hear that the synth 20 oil you use is the best thing under sun. Yes. it may be the best oil solution for your application, but it is not the optimal viscosity to prevent wear under all circumstances.

Clearly I wasted my time.


Easy there. What -- are you disappointed that there isn't complete agreement on this question? Or surprised? State your case, and be assured that others will state theirs. BTW, you're overextending what was said. I, for example, believe that 20s work very well in two of my three cars. But I don't think that anyone here (including me) has claimed that they're best for everything at all times. In essence, this is an impossible question anyway, since the answer will, almost obviously, be different for different cars and different situations.
 
Originally Posted By: friendly_jacek
Originally Posted By: Pablo

Bogus information alert!!!


Do you have proof that the information I posted is incorrect?

Yes, synthetic oils have corrosion inhibitors in them, but base oils have inferior corrosion resistance.

At least I have some evidence for my claims:

"Rust protection is achieved by metalworking fluid containing mineral oil. Synthetic lubricants do not provide proper corrosion protection." from http://www.substech.com/dokuwiki/doku.php?id=cutting_fluids_coolants

"Rust protection oils are commonly based on mineral oils (either paraffinic or naphtenic)." from http://www.substech.com/dokuwiki/doku.php?id=rust_protection_oils


First of all you made the claim, not I. If you make a claim, the proof is up to you. Those examples are totally irrelevant.
Quote:
Synthetic metalworking fluids are water based solutions (or emilsions) of synthetic lubricants (soaps and other wetting agents), corrosion inhibitors, water softeners, EP, anti-bacteria additives (biocides), glycols and other additives.
Synthetic fluids are supplied in form of concentrates, which are mixed with water before use.


Sounds to me like synthetic fluids get along just fine with water, but we both know you pretty much just demonstrated your google ability, not your knowledge base.

You wrote:
Quote:
...synthetic oils may fall short in corrosion protection as being more viscous in room temp, they will run down and expose metals


I await the proof.
 
---The viscosity must be matched to the bearing clearances. Bigger clearances need thicker oil, whether these bigger clearances are design or wear.

---Other things remaining equal, higher viscosity oil has higher film strength.

---Higher high temperature/high shear viscosity reduces wear but increases drag for increased fuel consumption.
HTHS @ 20wt > 2.59 millipascals
HTHS @ 30wt > 2.89 mpa
HTHS @ 0W-40, 5W-40, 10W-40 > 3.49 mpa
HTHS @ 15W-40 & higher > 3.69 mpa

---Larger bearing surfaces (with equal load) can use lighter viscosities.
 
Originally Posted By: friendly_jacek


Notice that 18 wheelers use 15W40 rather than 0W20.



My father just purchased a Cessna 400 this month. He took me to the hanger tonight to show me the plane. I found 1 quart of oil in the "trunk" of the plane. Exxon 20w50. Then it hit me.
All of the high-performance and heavy-load engines I have seen or researched use a higher weight oil. I'm sure there is a reason for this.

This is the engine it has

"TCM TSIO-550-C six-cylinder, fuel-injected, twin turbocharged engine with dual intercoolers, the Cessna 400 boasts a max cruise speed of 235 knots (435 km/hr) and a range of 1,250 nautical miles (2,315 km) at economy cruise speeds. So you'll cruise higher in one of the world's fastest single-pistons in the sky."

Exxon 20w50

I know you thin oil guys will call me ignorant and not knowledgeable, But.

I don't see a reason to use a lightweight oil unless you live in rigid cold weather. Do you guys really think you know more than the top engineers who design and test these (heavy-duty/high-performance) engines?!

Yeah, your toyota camry and ford focus say to use a 5w20. At the same time I turn my head to the tv and see a commercial of the camry boasting how it gets 1 mpg more than its competitor. Add in CAFE and it is obvious these low weight/low friction oils are just to squeeze out that extra MPG.

Some will say, "yeah Ford/Toyota have top engineers too and they know what is best for the engine!" Yep, they sure do have good engineers. But do you honestly think their goal is to spec an engine oil for the protection of the engine? [censored] no. They just care about sales, and right now, MPG sells.

I'm not saying your engine is going to [censored] out if you use 0w20. Because, well, they don't. They oil is "suitable." But, is it providing the best protection? I doubt it.

Your car may not tell the difference between 0w20 and 15w50. But that isn't the point. If the 0w20 provided better protection and was a "better" oil, if temperature permits, then these high-load/high-performance engines would spec an oil on the thin side of the scale. They would spec 0w10 or 0w5. But they don't. They spec an oil on the heavy side of the scale, 15w50's and 20w50s. You can't deny the "facts."
wink.gif
 
That aircraft and over the road trucks are operrated at near maximum output of the engines. You may not like your economy oif you extractred 80% or more of your capable power out of your personal conveyance.
Even my jeep spends 95% time at light load with small burst of high load. I can see how you came to your concluskion but I disagree on it based on duty cyles of the example engines.

Next time you are on the road try to time the percentage of time you have the trottle to the floor and report that as a percentage of time on the road. it shouldn't be much.
 
Quote:
I don't see a reason to use a lightweight oil unless you live in rigid cold weather. Do you guys really think you know more than the top engineers who design and test these (heavy-duty/high-performance) engines?!


Some of us see no benefit to heavier weight oils without a reason. None of us really thinks that we know more than the top engineers who design and test these heavy duty and performance engines.

Most of us don't drive truly heavy duty or performance engines, as much as we like to think so. Most of us who do, when engaged in truly heavy duty or high performance situations, follow the advice of those top engineers.

Quote:
Yep, they sure do have good engineers. But do you honestly think their goal is to spec an engine oil for the protection of the engine?


So I shouldn't listen to those good engineers, and only listen to good engineers that spec heavy oil?

Quote:
They just care about sales


I would hope that they leave that stuff to the marketing dept, but let be fair here, are you saying that engineers who spec heavy oils care less about sales? Buy it ..don't buy ..what do they care?
21.gif

Quote:

I know you thin oil guys will call me ignorant and not knowledgeable, But.


I term it a bit biased due to lack of experience base.
 
Originally Posted By: RI_RS4
Originally Posted By: friendly_jacek

The example of racing is poor as as racing is all about max power at the expense of wear. Racing engines are torn down after each race and rebuilt.


Wrong. In a 17 race season, a Formula one driver is allowed 8 engines. These engines are sealed prior to and after events. They may not be rebuilt.
Quote:
After consultation with the relevant engine supplier the FIA will attach seals to each engine prior to it
being used for the first time at an Event in order to ensure that no significant moving parts can be rebuilt or replaced.
Within two hours of the end of the post race parc ferme exhaust blanking plates (with one 10mm diameter inspection hole per cylinder) and further seals will be applied to all used engines in order to ensure that these engines cannot be run between Events. Upon request to the FIA these additional seals will be removed after the start of initial scrutineering at the next Event at which the engines are
required. All such engines must remain within the team's designated garage area when not fitted to a car and may not be started at any time during an Event other than when fitted to a car eligible to participate in the Event.


correct they are not rebuild but rather disposed of :)..

how many engines do you(or any of the people on this forum) plan on using in their cars this year?
 
So getting back to the original question, the optimal kinematic vis for minimal wear. Perhaps I should have said the optimal "minimum" viscosity because that's what we're really talking about hear. No offense to those in the thick camp but it seems kind of silly to see how thick an oil one can safely run with all the other negative attributes of running an oil heaver than necessary.

Pablo felt a 30 wt range of 9.3 cSt to 12.5 cSt as being too narrow depending on bearing size (width I presume) etc.
Would 8.0 cSt be a non issue? How about 6.5 cSt which happens to coincide with a couple of the lighter 20 wt oils available (eg RP XRP 5W-20 and 0W-10 of which their are a couple of excellent UOA's hear).
I'm thinking 6.5 cSt may be as low as you'd want to go before wear would start to ramp up? It may be OK to run oils into the 4 cSt range but wouldn't you be getting into frequent boundary lubrication with oil that thin by that time? Keep in mind we're talking maximum load situations; back out of the throttle and I would think vis of 2 cSt is no problem.

Maybe Gary Allen would know; has the SAE ever done tests of this sort?
 
Originally Posted By: CATERHAM
So getting back to the original question, the optimal kinematic vis for minimal wear. Perhaps I should have said the optimal "minimum" viscosity because that's what we're really talking about hear. No offense to those in the thick camp but it seems kind of silly to see how thick an oil one can safely run with all the other negative attributes of running an oil heaver than necessary.

Pablo felt a 30 wt range of 9.3 cSt to 12.5 cSt as being too narrow depending on bearing size (width I presume) etc.
Would 8.0 cSt be a non issue? How about 6.5 cSt which happens to coincide with a couple of the lighter 20 wt oils available (eg RP XRP 5W-20 and 0W-10 of which their are a couple of excellent UOA's hear).
I'm thinking 6.5 cSt may be as low as you'd want to go before wear would start to ramp up? It may be OK to run oils into the 4 cSt range but wouldn't you be getting into frequent boundary lubrication with oil that thin by that time? Keep in mind we're talking maximum load situations; back out of the throttle and I would think vis of 2 cSt is no problem.

Maybe Gary Allen would know; has the SAE ever done tests of this sort?


I think you are asking wrong question, HTHS viscosity is the one that has more impact on the engine wear.

You want to be above 2.6 HTHS in a regular use street driven car, but 3 would be better..high performance engines like > 3.5
 
Originally Posted By: CATERHAM
So getting back to the original question, the optimal kinematic vis for minimal wear. Perhaps I should have said the optimal "minimum" viscosity because that's what we're really talking about hear. No offense to those in the thick camp but it seems kind of silly to see how thick an oil one can safely run with all the other negative attributes of running an oil heaver than necessary.


I can't see the reasoning running the thinnest oil you can get away with just for a barely measurable fuel economy increase. You take away a lot of the safety cushion for pennies.
Originally Posted By: CATERHAM

Pablo felt a 30 wt range of 9.3 cSt to 12.5 cSt as being too narrow depending on bearing size (width I presume) etc.
Would 8.0 cSt be a non issue? How about 6.5 cSt which happens to coincide with a couple of the lighter 20 wt oils available (eg RP XRP 5W-20 and 0W-10 of which their are a couple of excellent UOA's hear).
I'm thinking 6.5 cSt may be as low as you'd want to go before wear would start to ramp up? It may be OK to run oils into the 4 cSt range but wouldn't you be getting into frequent boundary lubrication with oil that thin by that time? Keep in mind we're talking maximum load situations; back out of the throttle and I would think vis of 2 cSt is no problem.

Maybe Gary Allen would know; has the SAE ever done tests of this sort?


I would love to see how a 2cst oil protects the valvetrain. I would love to see it try and keep the rods and mains from going metal to metal. Even with your foot off the gas you've still got rpms and compression to deal with. You're just guessing here. And the 6cst number, where did that come from? There are tons of factors that determine what you can and can't get away with. Whether you want to admit it or not, a thicker oil reduces the chances and frequency of metal to metal contact period. I've seen it first hand many times from my own engines. But of course this doesn't matter. Only theory matters.
 
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