10W vs 10W-30 vs SAE 30 cylinder wear

[JAG]

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Please let me not be the only one that feels as though his/her head is spinning!

What I find strange is that in looking at some of the specs for a straight 30 wt oils, I find a HTHS of say 3.8, where as a multi-wt of say 5/10w-30 is around 3.2. In theory, the viscosity of the straight 30wt would be less as temperatures advance beyond 100c (lower VI), but yet the HTHS #'s are higher for the straight 30wt than for the multi-wt's.

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In the fluid mechanics use of the word "shear", the polymers make the oil they are in a "shear-thinning fluid". The faster it is sheared, the thinner it gets if all else is constant.

Can get a rough relative estimate of how much polymers are used in an oil by calculation the ratio:
(Kinematic Viscosity @100C) / (HTHS Viscosity)
The larger the ratio the more polymers are used, generally. TooSlick is the guy I first saw use this quantity.

 

[Curious Kid]

Cold flow aside, I suppose a vehicle's manufacturers recommendation against the use of a straight wt oil would likely be leaning towards increasing operating efficiency, but heck I'm just trying to learn here so I'll step-off the box - I'd like to do more with less also.

Concerning the graphical data (which I'm thinking is more and more useless due to the lack of oil composition information, possibility of too light a wt of oil as some have speculated, etc.), I thought how counter intuitive it seems with test data from another study that had measured thicker oil films reaching the upper piston rings as the oil grade used dropped (15w-40 to a 5w-20). But again the rate of shear could account for breaching this "thicker" film...less lubricating base oil and more faux viscosity building additives.?.

As someone briefly mentioned earlier in this thread, I too would like to see more accurate viscosity grading for oil in real situations, rather than based on how they flow down a tube at a give temp. under gravity's pull, or was that a steel ball through the fluid...in any event, I think it's safe to say we are not the average owners of engine powered machines.

Again, interesting thread.

Take care.

 

[JAG]

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As someone briefly mentioned earlier in this thread, I too would like to see more accurate viscosity grading for oil in real situations, rather than based on how they flow down a tube at a give temp. under gravity's pull, or was that a steel ball through the fluid...

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That's being worked on currently. Let's hope they succeed and it gets incorporated into API and ACEA specs.

BTW, the viscosity of some motor oils can quadruple when subjected to pressures that can be found in journal bearings. This pressure-viscosity response is just as important as the shear thinning (or lack of) response. Different motor oils have different pressure viscosity responses so it's a variable, not a constant among them all. The source of this is the article mentioned here:
http://theoildrop.server101.com/forums/s...ge=0#Post936268

 

[Curious Kid]

Another question - There are two oils of like viscosity at 100c, one a straight wt and the other a VII enhanced multi-wt. As they cool down from 100c, they both thicken. When under equal conditions of stress, could it be that the VII enhanced oil shear more than the straight-wt, even if they had both were cooled to a point so that their viscosities were equal prior to stressing? As I'm thinking this through, it seems obvious that such could/would be the case, and would seem to be backed by the graph at the beginning of this thread. Might it then be safe to say that start-up wear due to inadequate film protection prior to REPLENISHMENT flow induced by the oil pump. the time delay for shear/bleed-out replenishment is an area where a multi-wt oil is beneficial, but potentially at the compromise for an increase in bleed-off rate increase. It's a balance with potential trade-offs in given situations I suppose. Like everything, there's an aspect of compromise.

Interesting.

Take care.

 

[Curious Kid]

Thanks for reminding me of that JAG.

So many points/aspects to something some think so simply as lubrication (I too was one of those individuals. I'll admit, things seemed much simpler then, but I definitely think I knew less about what I was doing, urh, well now I'm hesitant and scratch my head a bit more.

Take care.

 

[JAG]

I don't follow ya in your post two posts up but that's ok. I saw in that other thread on VIIs that there seems to be confusion on shear thinning. It occurs without the polymers breaking apart; shear thinning does not mean the oil has permanently lost kinematic viscosity. It is simply how the oil behaves immediately when a high shear rate is imposed on it. It is the opposite of a shear thickening fluid. Google these terms to get better descriptions than I can give.
This Blackberry is hard to type on!
Oil pressure drop is from permanent viscosity loss. Shear thinning is immediate.
This post may suck...blame blackberry.

 

[Steve S]

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According to this chart SAE 30 provides better protection even at low temperatures between 20 -30 degrees Centigrade. That's contrary to all I've ever read.

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What have you read?

 

[G-MAN]

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According to this chart SAE 30 provides better protection even at low temperatures between 20 -30 degrees Centigrade. That's contrary to all I've ever read.

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What have you read?

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Dr Nip/Tuck's articles?

Just picking at you, Dr Haas.

 

[Curious Kid]

Driving home from work the other day I pondered the graph and questioned, temperature relationships with additive effectiveness aside (and of which like/dislike type/quantities are unknown), I wondered if the viscosity of the non-VII ladened straight wt oil tracked well with the clearances of the piston to cylinder wall as they mutually warmed and altered themselves (oil thinned, clearances decreased, etc.)? Shock loads upon the VII ladened oil (10w-30) could likely have aligned so as to lessen the viscosity value regardless of the oil films temp, approaching the base oil's true viscosity.?. The mono 10wt seeming just to thin, until what in both cases reaches a near commonality for all wt's, which happens to be what might be deemed a sweet spot for additive activity. For the 10w-30 and especially the lighter 10wt mono that could be benefiting most from the wear control additives in the optimal operating temp range, I only wonder just how long such low wear rates could be maintained before it would increase substantially - that is if such is the case of course. I also wonder over how long a period this test was in order to collect such comparative values".

If the link for decrease ring-cylinder wear control benefits could be attributed to the oil visc and clearance change relationship relative to temperatures, that would be most interesting. Such an oil's use however with journal bearings I could only think would suffer more from potential starving situations in cold start situation as they become further from the pump, but what do I know. I wouldn't think there would be as much a change with journal clearances as there are piston to cylinder, but there as well, I don't know...only presume.

Pure speculation...I seem to spend a lot of time doing such. It at least keeps me out of trouble, I think.

Take care.

 

[bruce381]

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From memory using a OCP liquid VII
10/40 about 10%-12%
5/30 about 7%-10%
15/40 about 5%-7%
10/30 about 5%-7%
20/50 about 5%

depends on base stock
bruce

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Any thoughts on how these might change with a good Grp III or IV base? Or are those included in the above?

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Higher VI oil would use less perhaps 10% or so less
bruce

 

[G-MAN]

From Bruce's answer, I would infer that with a fully formulated synthetic PCMO where the fluids used in the base oil blend all have a VI of >140, only the following grades will have some VI imporver--probably in the 2% to 15% range:

0w30
0w40
0w50
5w30
5w40
5w50
10w40
10w50
10w60
15w40
15w50

I would add that ANY oil where the base oil used is predominately Group III will probably have some VI improver no matter what the VI of that Group III is.

 

[buster]

G-MAN, you're probably right but I was told Amsoil 10w-30 with a VI of 171 does contain some VII's and so does Mobil 1 10w-30. However, both contain a small amount.

Only synthetic grades I know of that don't use any are RL.

 

[SpitfireS]

Great post, very informative!

Would the same apply for straight weight gear oils?
My manual specificly specs a SAE 90 GL-5 for the diff.
No 75W-90 or anything like that.
Straight weight SAE 90 oils are not available at every automotive parts store so many go for the 75W-90 or 85W-90 gear oils.
IMO Honda specs the straight SAE 90 for a reason.

But I'm not trying SAE 30 in my F20C2 engine.
Maybe if I lived in the Sahara.
Or if the car was used as a weekend car, stored and started in a heated garage.

 

[ericthepig]

What about mixing 3 qts straight 30 to 2 qts 5w30 (same oil brand) - wouldn't this give something in the range of 15w30 (which eases the nerves on start-up issues) and yet gives the oil much of the straight 30 backbone. (?)

 

[Master ACiD]

i wouldnt worry about mixing sae30 to lower the cold viscosity too much. i just pulled up a msds of pennzoil sae30, 5w30 and 15w40.
the sae30 has a viscosity of 97cst at 40C. thats thinner than their 15w40 which has a viscosoty of 118 at 40C.
the pennzoil 5w30 is 64cst at 40C and thats not much lower than the sae30.

the pennzoil sae30 has a pour point of -30C, the 5w30 is -39C, the 15w40 is -33C.

im not an oil expert like some of the other guys here, but i dont think youll gain much by dilluting an sae30 with a 5w30. but then again i only did a quick look at pennzoil brand. others may be different.

 

[Gary in Sandy Eggo]

Didn't read all the posts, but enough to ascertain some common questions regarding mono-grade oils. If anyone remembers, I've consistently opined that best protection against wear will be provided by a mono-grade oil. I run SAE-30 in my Grand Prix in the summer, and sometimes use 10W-30 in the winter months.

1. Mono-grade oils provide superior metal-to-metal protection because they provide MORE oil between the moving parts than do multi-grade oils.

2. Multi-grade oils are made up of the lower number viscosity oil, and utilize VI improvers to "simulate" a thicker oil at operating temperatures. These VI improvers do nothing to lubricate, and displace oil which does lubricate.

3. VI improvers break down in use causing the oil to "simulate" a thinner and thinner oil until it finally acts like a straight lower number oil even at operating temperature.

4. You need viscosity to act as a cushion between moving parts. The more the viscosity, the more the cushioning affect. However, if oil becomes too thick at operating temperature, cylinder wall wear will increase due to insufficient oil throw-off from the bearings.

5. Big radial and other reciprocating aircraft engines demand mono-grade oils because of the aforementioned problems with multi-grade oils, AND the fact that those broken down VI improvers will slip past the rings and foul the spark plugs. Things may have changed, but as recent as 10 years ago, synthetic oils were to be avoided in radial engines because they're not robust enough.

6. Lawn mower and other small air cooled engines have for decades specified mono-grade oils, citing excessive oil consumption with multi-grade oils. This is because the multi-grade oils break down, thin out, and slip past the rings and are consumed. The small reservoir in small engines cannot tolerate much oil consumption before they're out of oil.

7. SAE-30 oil can be safely used in automobile engines down to a start-up temperature of 40F. Below that you should use a multi-grade oil, even though it provides less engine protection at operating temperature.

8. My Suzuki Intruder 1400 motorcycle specifies 10W-40. I run straight SAE-40, HOWEVER, I am anal enough to preheat the engine with a shop light under the engine overnight before taking it out, AND, I always run up a minimum of 140 miles for each "cold" start. In addition to preheating, I keep my rpm's below 2500 rpm for the first 5 miles. If I were doing a lot of shorter rides, I'd be running SAE-30 in the motorcycle. Relative velocity between moving parts determines wear rate when lubrication is marginal.

I've called 0W-20, 5W-20, and 5W-30 oils wee-wee. So, I won't repeat that here.

Regards, Gary in Sandy Eggo

 

[buster]

In theory I think you are probably right, but I haven't seen any evidence that multi-grade oils are any worse than straight grades. UOA's of modern SM multi grade oils including 5w-20's are outstanding, unless UOA's don't show the whole picture. Wear metals are so low with most oils under normal drain intervals I don't see the need for a straight grade.

In climates like "A whale's ----", you can get away with a good straight grade but in very cold weather, I'd want a multi grade.

 

[Tempest]

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Things may have changed, but as recent as 10 years ago, synthetic oils were to be avoided in radial engines because they're not robust enough.

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I'm not an aircraft guy, but that sounds rather odd.

 

[G-MAN]

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7. SAE-30 oil can be safely used in automobile engines down to a start-up temperature of 40F. Below that you should use a multi-grade oil, even though it provides less engine protection at operating temperature.

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Ten years ago I would've agreed with you. But I think a modern SAE 30 blended to meet SM specs is good down to at least 32F, with mid 20s not being out of the question.

 

[buster]

G-MAN, why do you think then that most racing oils are multi-grade such as M1R? Or, are most racing oils VII free? I can only think of RL that uses straight grade. And then you have Eneos with their 0w-50? Obviously VII's.