FAQ - Thin Oil Myth

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Hi. I would appreciate you experts here to tell me which is a better oil based on these data alone and the reason why. I am keen to learn. Much appreciated.


Mach5 10W30
Density @ 15 °C, kg/l 0.8636
Pour Point, °C -33
Flash Point, °C 228
Kinematic Viscosity, cSt @ 40 °C 72.9
Kinematic Viscosity, cSt @ 100 °C 11.2
Viscosity Index 146
Cold Cranking Visc, cP @ - 25 °C 4,130
Sulphated Ash, %wt 0.81
TBN, mg KOH/g 6
ASTM Colour 3.5
API SL/CF
ILSAC GF-3
ACEA A3-98


Syntium800 10W30
Density @ 15 °C, kg/l 0.8635
Pour Point, °C -33
Flash Point, °C 228
Kinematic Viscosity, cSt @ 40 °C 74.0
Kinematic Viscosity, cSt @ 100 °C 11.2
Viscosity Index 141
Cold Cranking Visc, cP @ - 25 °C 4,840
Sulphated Ash, %wt 0.82
TBN, mg KOH/g 6
ASTM Colour 3.5
API SL/CF
ILSAC GF-3
ACEA A3-02
 
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BUMP ... maybe a mod/admin would consider making this thread "sticky"?




A great idea!
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Larry, you are referring to a Pour Point Depressant, not a VII. Different molecules, different results.




No he is NOT talking about PPD's. He is referring to starting with an extremely thin oil that would be significantly thinner at startup than even a 0w rated oil, then adding VIIs to make it act like a 30wt oil at operating temp. If he were talking about PPD's, he would have said "why not add something to a 0w-30 oil to make it like a -5w-30" or something of the like. Reading is Fundamental.
 
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So can anyone explain to a newb how 5W-20 oils compare to 5W-30 oils when hot?



Sure, in simple terms the 5W-30 is thicker than the 5W-20 oil. Here's a viscosity table which gives more detail:
viscosity_table.jpg


And a viscosity grades chart:
SAE_J300_Viscosity_Grades.gif


Hope this helps.
 
cool.
all i know is that my Galant doesn't mind 5W-30 but boy does she hate 10W-40! dropped that out of her tonight, after less than 200 miles....tick was still loud as can be, so the thicker oil didn't help...let's hope ARX does.
 
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Larry, you are referring to a Pour Point Depressant, not a VII. Different molecules, different results.




No he is NOT talking about PPD's. He is referring to starting with an extremely thin oil that would be significantly thinner at startup than even a 0w rated oil, then adding VIIs to make it act like a 30wt oil at operating temp. If he were talking about PPD's, he would have said "why not add something to a 0w-30 oil to make it like a -5w-30" or something of the like. Reading is Fundamental.




And a Fundamental realization that there isn't a Minus 0 rating would make the poster's comment more clear. To answer Larry's question: taking a thin oil and adding Viscosity Improvers is exactly what many oils have done to them...when those VI's degrade or shear, they become thinner at operating temps. Many highly refined/developed oils' viscosity can span their rated range with no VI's...that's one of the reasons these oils (often called "synthetics") are considered to be "better".
 
I come across the "5W-30 is too thin, so I use 10W-30" all of the time. Lots of time its from an auto mechanic. What are the odds I'll ever get them to look at a chart for the "W" winter grade guidelines? So I just tell them that the part WITHOUT the "W" is taken at high temperature, around 210 degree F. Once I see comprehension in their eyes I then proceed to tell them the "W" part is taken at a lower temperature and measures how much thickening occurs. I let them know there is a scale used to measure this and just give them a few examples. What I come away with a having someone understand for the first time that oil isn't measured at room temperature and the "W" part may be a good thing if the temperature drops depending on how much.

You'd be surprised, (maybe not some of you) at how little the average person knows about motor oil viscosity. Every little bit helps.

The information provided above was great.
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Yes, 0W-30 can be thicker at operating temperature than a 10W-30. It all depends on how much VI improving polymers are added to the base 0W oil and how much less is added to the 10W oil. However, what this entire analysis ignores is the viscosity shear-down at operating temperature that occurs in all oils using VI improvers. The more improvers are used, the faster the shear-down. 0W-30 will have more VI improvers than 10W-30.

Someone on this board sent me to a dissertation on thin oils about a year ago. Thank you. However, being a dinosaur, I cannot be convinced that thinner oils provide as much metal-to-metal separation as thicker oils. Additives that "sacrifice" themselves in metal-to-metal contact are a poor substitute for keeping the moving metal parts from touching in the first place.

Why do you think they have a "high-mileage" version of multigrade oils for cars over 65K miles. The wee-wee you've been putting in your car engine has allowed more wear, and now you've got to use thicker oil just to fill in the "gaps" between the moving parts.
 
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However, what this entire analysis ignores is the viscosity shear-down at operating temperature that occurs in all oils using VI improvers. The more improvers are used, the faster the shear-down. 0W-30 will have more VI improvers than 10W-30.



I'll agree that this is generally true. However, I wouldn't make this blanket statement because there are exceptions. (Redline Oil comes to mind.)

As a personal experience, my 0w-30 oil stayed in grade better than my 10w-30 oil. (I'm intentionally leaving out the brand(s), I don't want any bashing.) And you'll find that many oils with a wide viscosity range won't "shear-down".

The point of this write-up is to dispel the myth that certain oils are "thin". I'm not promoting the use any specific oil, just trying to deliver some facts.

And for those who missed it:
MANY other factors about oil were not discussed here. Please don't base your oil preference on viscosity numbers only.
 
what people don't understand is that in the old days, visc made a big difference as far as protection. why? because it was acting like a barrier additive. it was thicker and it took more pressure to squeeze the oil out between the parts. therefore it protected more. now, we have better barrier additives and no longer have to use as thick of oil as we use to. we now get better protection in a lower visc oil but also get better gas mileage because it takes less to move the oil unlike the thick oil we use to use. visc use to play a big role in protecting an engine but now, along with visc, additives make a big difference as well.
 
Very good and simple explanation. I think the definition of thinner or thickens less it like 6 of one and half dozen of the other.
In case anyone wants to make their own graph, click here and supply your own viscosities: (even though it is spanish, I think you can figure out how to use it)
http://www.widman.biz/Seleccion/Viscosidad/Conversiones/Graficos/graficos.html

I'm sure pour point depresants modify the low end a little. That is a straight calculation based on viscosities input.
 
Bob:

Well put. For whatever reason, there seems to be a great deal of "retro-think" with respect to engines, oils, and their characteristics. Another factor that really come into play in the last decade or so is the improvement in metalworking and machining, which has allowed tighter clearances, made to very close tolerances.
 
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