oil weight
Post Fiend
Joined: Jun 2001
Posts: 5,228
Likes: 5
From: Running Springs CA
By heavier, I assume you mean thicker (viscosity) and not density (specific gravity). When measured at the boiling point of water, 100C,
30 thinest
40, 15W-40 middle (both are the same at 100C)
20W-50 thickest
At 40C, a purely arbitrary number for caluclating Viscosity Index, for Chevron dino,
30 is again the thinnest
15W-40 is next
40 is next
20W-50 is thickest
Cold Cranking Viscosity is not published for straight grades, so a comparison is difficult, but the pour points (temperature at which you can barely pour it) for Chevron dino are,
15W-40 -38C
20W-50 -21C
30 -18C
40 -12C
I hope this helps.
Jim
30 thinest
40, 15W-40 middle (both are the same at 100C)
20W-50 thickest
At 40C, a purely arbitrary number for caluclating Viscosity Index, for Chevron dino,
30 is again the thinnest
15W-40 is next
40 is next
20W-50 is thickest
Cold Cranking Viscosity is not published for straight grades, so a comparison is difficult, but the pour points (temperature at which you can barely pour it) for Chevron dino are,
15W-40 -38C
20W-50 -21C
30 -18C
40 -12C
I hope this helps.
Jim
Postmaster
Joined: Dec 2003
Posts: 2,659
Likes: 2
From: S/C Texas
Originally Posted by DT 466Man
yes it does i just wanted to make sure thats the way it went.
I kept getting confused on all the other topics sayin 10 is the weight an 30 is something different in 10w30
thanks
I kept getting confused on all the other topics sayin 10 is the weight an 30 is something different in 10w30
thanks
Just as 20w50 is a 20 weight with VI's to move it up to a 50 weight at 100*c.
I dont know if that helped clear up a little of your confusion....but its okay..I just wanted to hear myself talk.
Post Fiend
Joined: Jan 2000
Posts: 5,860
Likes: 4
From: Metro Detroit (Redford)
I'm not so sure the "w" number is a good estimate of the base oil weight. For example, Valvoline tech sheets for All-Fleet Plus Engine Oil show a grade, 10w. That's it, just 10w. It lists a 100C viscosity of 6.4. A straight 20 weight oil by the API engine oil classification runs from 5.6 to < 9.3, so I would say the All-Fleet Plus 10w is a thin 20 weight, or one could say a 10w20.
The FAQs of the European Redline Oil web site say that a straight 30 weight will pass a 20w winter test and so is really a 20w30. Then add some viscosity index improvers and you get 20w50.
So it seems a 20w50 has a base oil in the 30 weight cateory, and a 10w30 or 10w40 appears to have a 20 weight base oil. Wonder what the 5w30 is?
But really I don't know. Just some info I have located. Would love to have an oil company chemist tell us how it really is.
The FAQs of the European Redline Oil web site say that a straight 30 weight will pass a 20w winter test and so is really a 20w30. Then add some viscosity index improvers and you get 20w50.
So it seems a 20w50 has a base oil in the 30 weight cateory, and a 10w30 or 10w40 appears to have a 20 weight base oil. Wonder what the 5w30 is?
But really I don't know. Just some info I have located. Would love to have an oil company chemist tell us how it really is.
Post Fiend
Joined: Jun 2001
Posts: 5,228
Likes: 5
From: Running Springs CA
They use a blend of different base oils in a multigrade, not just a single one like 7cst, for example. The Chevron base oils site gives some limited explanation. Thinner base oils are designated by cst viscosity and thicker ones by SUS, further confusing the matter. This is just one of those industry conventions that evolved over time.
Jim
Jim
Post Fiend
Joined: Jan 2000
Posts: 5,860
Likes: 4
From: Metro Detroit (Redford)
Originally Posted by jimandmandy
They use a blend of different base oils in a multigrade, not just a single one like 7cst, for example.
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Senior User
Joined: Jun 2003
Posts: 380
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This does not explain in full but all these oils are not created equal .
10w-40's range from a vi of 73@40c " 104F " to over 100@ 40c . This affects fuel mileage during the warm up phase and pumping ability when cold .
The pour point on the data sheet is nearly worthless for most of the USA .
As far as straight wts go , the makers of dino's don't even offer CCS data for them but to give you an idea on the bottle of Castrols 40wt they have written not for use under 60F , the straight 30 wt not under 40F .
That 15w in front of diesel oils is flat decieving IMO . It's very thick and a poor choice for short trippers when cold . Actually for gas motors there's near always a better choice than those oils unless one lives on Venus
Please don't mistake me for a thin oil lover . Oil is a tool . Pick the right one for the job . No pliars on the wheel lugnuts ect .
10w-40's range from a vi of 73@40c " 104F " to over 100@ 40c . This affects fuel mileage during the warm up phase and pumping ability when cold .
The pour point on the data sheet is nearly worthless for most of the USA .
As far as straight wts go , the makers of dino's don't even offer CCS data for them but to give you an idea on the bottle of Castrols 40wt they have written not for use under 60F , the straight 30 wt not under 40F .
That 15w in front of diesel oils is flat decieving IMO . It's very thick and a poor choice for short trippers when cold . Actually for gas motors there's near always a better choice than those oils unless one lives on Venus
Please don't mistake me for a thin oil lover . Oil is a tool . Pick the right one for the job . No pliars on the wheel lugnuts ect .
Last edited by DOHC; Sep 5, 2004 at 06:49 AM.
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Senior User
Joined: Jun 2003
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Originally Posted by peppy
Okay, the oil giants have lied and decieved us again. How so?
I'll just set back and let you tell me how exceptionaly well these type oils perform when cold ....... in engines , not on paper .
I'm certain I'll be set straight for my oversight
Postmaster
Joined: Dec 2003
Posts: 2,659
Likes: 2
From: S/C Texas
Dont go and think I know what I'm talking about. 
In s/c Texas.....I have no idea how well they perform in the cold.
I thought you were saying its not really a 15w oil.
I dont use it for the 15w.....I use it for the 40 weight, and the additives.
I hear from so many directions how 10w40 has more degrading qualities, than not. I know I cant use a straight 40w all year. So I went with the 15w40. A significant improvement for my situation.
Again, not to get any feathers ruffled.......I thought you were saying its not really a 15w. I missed the implication of 15w not flowing when cold.
Cold down here is 30* Cold in my world is springtime for many.
In s/c Texas.....I have no idea how well they perform in the cold.
I thought you were saying its not really a 15w oil.
I dont use it for the 15w.....I use it for the 40 weight, and the additives.
I hear from so many directions how 10w40 has more degrading qualities, than not. I know I cant use a straight 40w all year. So I went with the 15w40. A significant improvement for my situation.
Again, not to get any feathers ruffled.......I thought you were saying its not really a 15w. I missed the implication of 15w not flowing when cold.
Cold down here is 30* Cold in my world is springtime for many.