Why use thicker oil?

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Originally Posted By: crinkles
doug, how can I get to the HTHS requirement for my engine? I have never seen it required for my car, could it be inherent in the requirement for SM/ILSAC GF4 oil? THen again i see generally the HTHS being lower for lower viscosity oils (in general)
The owners manual suggests an adequate oil recommendation.
 
Originally Posted By: AEHaas
"High pressure helps to keep metal parts like the bearings out of contact with each other"

This is not my statement.

aehaas



It is a direct quote of your quote in chapter 9 of this.
http://www.focfloridaregion.com/

You then went on to elaborate on it.
 
Originally Posted By: Steve S
Originally Posted By: crinkles
doug, how can I get to the HTHS requirement for my engine? I have never seen it required for my car, could it be inherent in the requirement for SM/ILSAC GF4 oil? THen again i see generally the HTHS being lower for lower viscosity oils (in general)
The owners manual suggests an adequate oil recommendation.


+1

To elaborate a bit, the oil viscosity spec used by API rated oils is SAE J300. SAE J300 specifies a minimum HTHS for each viscosity oil.

The European oil specs do it differently, but the HTHS requirement is still in their spec.
 
In the olden days before the internet I hotrodded engines in cars and boats ,we would pick the oil viscosity by the oil pressure and depending how the engine was used . Mom driving to work would get a 10w30 The oil would not get really hot as the engine was not asked to put out a whole lot of power.The pickup pulling a 5,000 lb trailer to the mountains would get a 20w-50 because the oil pressure would drop below the mfgs recommendations with a 10w-30 because the oil would get real hot. I learned about that in auto shop in high school. And going to the auto programs to keep up my skills with all the new technology. The engine machine finishes are different in the newer engines the tolerences are tighter as well as many clearances to meet the emission requirements. Most people have no idea how the emission warranties have benefitted average engine life. And the latest comp controls control so much that the pressure on the crank is smoother and individual cyl pressure can be controlled which can keep the pounding to the rods and crank bearings to a minimum.
 
"High pressure helps to keep metal parts like the bearings out of contact with each other"

This is not my statement.

aehaas

From XS650: It is a direct quote of your quote in chapter 9 of this.
http://www.focfloridaregion.com/
You then went on to elaborate on it....

My comment to all of the above - Before you make statements as this it is helpful to read everything. Some material I wrote was edited by the web master at that particular Ferrari web site. Furthermore, "High pressure helps to keep metal parts like the bearings out of contact with each other" was quoted in that passage as it was a statement by Another person. I then submitted information that showed the importance of flow and not pressure and I showed how pressure in a sealed bearing has no effect on wear.

It is best to ask others for clarification before you condemn them outright.

aehaas
 
Start up wear is really simple . I like to keep things simple cause that is what I am. The engine not running the bearings are touching .So untill the bearings get enough oil and enough speed to start a hydrodynamic state there is wear .Think water skiing ,your are in shallow water by shore touching the bottom when you start to move it takes a movement before the ski gets off the bottom then in a bit the ski is planning thich seperates you from the lake bottom by a layer of water. Then there is the time for the oil to reach the pump ,with the wrong viscosity oil for the starting temps there could be increased wear for example a 30wt in 0*f temps think sucking a thick milkshake through a thin straw .if it takes a long time there will not be enough or any oil for a while so there will be more wear . Then there will be the temperature activated additives and the pistons aren't round untill warm and the clearances are different so the cyl aren't sealing as they can and the air fuel mixture is richer and there is more blow by which increases piston and piston ring to wall wear Bla bla bla .That is why an over the road semitruck engine last way longer than an around town pickup and delivery semitruck engine.
 
Originally Posted By: AEHaas
"High pressure helps to keep metal parts like the bearings out of contact with each other"

This is not my statement.

aehaas

From XS650: It is a direct quote of your quote in chapter 9 of this.
http://www.focfloridaregion.com/
You then went on to elaborate on it....

My comment to all of the above - Before you make statements as this it is helpful to read everything. Some material I wrote was edited by the web master at that particular Ferrari web site. Furthermore, "High pressure helps to keep metal parts like the bearings out of contact with each other" was quoted in that passage as it was a statement by Another person. I then submitted information that showed the importance of flow and not pressure and I showed how pressure in a sealed bearing has no effect on wear.

It is best to ask others for clarification before you condemn them outright.

aehaas



It was clear and incorrect, no clarification was needed.

It was an article with your name on it that has been there for some time. If you disagreed with with the editors work, you should have had it corrected.

Quote:
I showed how pressure in a sealed bearing has no effect on wear

And the connection between that and the topic at hand is?
 
Q. [/quote]

It's no myth, I've seen the better protection offered by thicker oil first hand from my own teardowns. You're able to "get away" with thinner oils today due to the reasons you mentioned. It doesn't mean thicker oils don't protect better in some cases. [/quote] Well yeah your putting out over twice the factory H.P.Pounding the living snot out of that cute little crankshaft ,Those engines are IMO quite incredable, one of the engines G.M. was dumb enough to eliminate from their line up.
 
This has been an interesting thread and I picked up on a few things I did not know and really appreciate that.

I have an engineers intuitive opinion about 30 weight vs 50 weight oil. I understand a 50 wt grade is generally recommended for engines that run really hot, or really worn out. Air cooled engines in particular will run hotter crankcase temperatures and benefit from the higher vis oil. Of course one way to cool the engine oil down under demanding conditions in lieu of higher viscosity is install an oil cooler.

I think our oil pumps are essentially linear displacement, double the RPM you double the flow. The engine oil distribution system has a fixed Cv (the effect of centrifugal force in the crank may influence the apparent Cv at higher RPM). So as flow rate goes up so do the pressure losses to accommodate the higher flow. At some point the oil pump relief valve sees this and progressively starts bypassing some oil to maintain the preset pump discharge pressure. Higher vis oil also increases pressure losses. So my theory is a given motor, with 30 weight will deliver more flow to the bearings, cam and valve train, than the same engine running 50 weight. The contribution to oil temperature build up will be less for the 30 wt too, since less oil is being bypassed across the pump(?).

So am I all wet here?
 
If the 50w is really really hot it could be thinner than a 30 wt that is not very hot. I am not exactly where it is but there was a viscosity calculater where you plug in the temps and viscosity and get the viscosity at certain temps. I am just too dumb to get it all together . But everything changes with temps and rpms and the load on the engine. Engines are pretty flexible and stand up to our abuse otherwise they wouldn't give an average long life.
 
Originally Posted By: Steve S
[/quote]Those engines are IMO quite incredable, one of the engines G.M. was dumb enough to eliminate from their line up.


^^Yep,GM`s biggest mistake. Discontinuing probably the best engine on the planet.
 
Originally Posted By: Throckmorton
Originally Posted By: Quest
remember the catchword: "May"....

Recall the SAE paper submitted by Honda Engineers RE: 0W20 on HOnda engines in late 90s (around 1998 or 99), Honda and a few other developments already working hard on using lower viscosity grade motor oil in the engine designs.

Also: due to technical progress made in IC engine developments during the past 20yrs or so (simply by looking at the rod/big end bearings and the materials it used will tell you a lot), improvements in manufacturing process, computerised engine control (which dramatically reduce fuel-related oil dilution/contaminations, more precise mixture control, etc.), etc. is what makes using "thinner" motor oil possible.

Unfortunately, avg joe on the street, as well as a lot of mechs are still falling behind in fully understanding this matter ....thus the urban legand remains.

19.gif


Q.
Do you have a link to this paper?


Merry Christmas.
http://cid-ada1e19227939272.skydrive.live.com/self.aspx/Public/SAE 0w20.pdf
 
Wow, I'm almost afraid to post.
crazy2.gif


Hey Army_guy, if you plan on beating your Jeep, run a 40wt. As a fellow Jeeper, I typically run a SAE30 or 10/15W40 in my 2.5L & 4.0L Jeeps during the spring/summer/fall months. I've had some pretty good UOA results in my 2.5L Wrangler trail rig despite the beatings it sees. This is sometimes in hot temperatures, in compound low-range, spinning either 35" or 38" tires. The last time I used 10W30 under these conditions, I burnt the rings in all four cylinders. When I disassembled that engine, the main and rod bearings were in pretty decent shape. The rings, obviously, were toast. I attribute this to the instant shearing that occurred at the rings. I haven't had any issues at all running the thicker oils. Oh, the 10W40's usually sheared to a high 30wt too and I also never exceeded the factory 5500 RPM redline.

These conditions are pretty extreme, however, consider that the same engine can survive on a 10 weight oil (ask Gary Allen) in average conditions. Running a 20 weight in an old tractor engine is nothing new either. People have been doing it since the 30's. It's the conditions in which it's used. There's no doubt that today's engine management and cooling systems kick bum. They keep the coolant and oil temperature pretty stable even during the harshest conditions. This, in addition to the level of engineering built into 20wt oils, lets you have great economy while providing great protection.

So, what do the four pages of poop in this thread mean? IMO, if you beat your Jeep during the wheeling season, run a 40wt. In winter, I run 5W30. 4.0L's typically have better UOA's on 40 weights, however I've seen an excellent report a couple years ago with Havoline 10W30. If I had a daily driver which I could stop myself from lifting w/ larger tires, I would try a 30 wt and get a "feel" for what works.

I hope what I wrote makes sense. It's been a long day and I'm beat.

Happy Trails.
 
Originally Posted By: Steve S


Q.


It's no myth, I've seen the better protection offered by thicker oil first hand from my own teardowns. You're able to "get away" with thinner oils today due to the reasons you mentioned. It doesn't mean thicker oils don't protect better in some cases. [/quote] Well yeah your putting out over twice the factory H.P.Pounding the living snot out of that cute little crankshaft ,Those engines are IMO quite incredable, one of the engines G.M. was dumb enough to eliminate from their line up. [/quote]

"Cute little crankshaft" is being too nice. Everytime I see the spares on the shelf I get a chill knowing that's what's in my car.

And I admit in most of my thick oil/teardown posts that I have unique problems. The crank flexes, the main caps walk, everything moves around and this is probably why I *have* to use a 20-50.

My father's built stage II block (4 bolt), forged internal 4.5L GN runs a 15-40 and has had no problems with nearly 1.5 times the hp of mine.
 
Originally Posted By: Doug Hillary
Hi,
crinkles - Yes it is inherent in the lowest viscosity lubricants specified for your engine

The ACEA Quality system's coding system is more transparent - eg A1/B1 should not be used where a A3/B3 lubricant is specified
They state clearly that "These oils may be unsuitable for use in sme engines. Consult owner manual or handbook if in doubt"

As an example an A1/B1 0W-20 viscosity lubricant will have a HTHS viscosity around 2.6cP. You will not find that viscosity lubricant with a A3/B3 ACEA Quality rating (3.5cP)

Where a Euro manufacturer has a minimum HTHS viscosity it will be spelled out in the need to use a A3/B3 (example) lubricant and internally. It is covered in the manufacturer's Approved lubricants List


thanks doug I am beginning to see the light...
 
Here`s something I read in my friend`s new Mustang V6 owner`s manual:

V6 models-5W30
V8 models-5W20

Why would they recommend a 30 weight in their V6 and a 20 weight in their V8,BUT the Ford GT recommends a 50 weight (5W50)?

Are they trying to squeeze as much gas mileage out of their most popular car (Mustang GT) to boost it`s sales? I`d think a 20 weight would be recommended in their V6 over their monster V8 motor. Just a thought.

On a side note,that V6 Mustang runs like a beast! Sounds nice and throaty like a V8. I was VERY impressed! First time I`ve ever been in one. That car`s so comfortable it felt like I was sitting in a Lazy Boy recliner!
 
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