Can some one explain the oil grades to me? Like 0W30 20W50

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As the title says, what do these numbers mean? I always thought that the higher the number the thicker the oil and the thicker the oil gets the more protection (oil film) it provides. For example 0w30 provides a very watered down layer of protection vs. thicker oil such as 20W50. I also understood that the hotter the engine gets the thiner the oil gets! Based on these assumptions I figured using 20W50 in summer and 10W40 in winter is best setup for Vw engines. Is this correct?
 
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A 0w30 oil is one that "behaves" in cold weather like a 0 weight oil, and in hot weather it "behaves" like a 30 weight oil, or more accurately at high temps it behaves like a 30 weight. This is the way a multi-grade oil is designed to function. If it's a well built oil, a 0w30 will provide the same protection at high temps that a straight 30 weight would, but in cold weather, where the straight 30 would be so thick it wouldn't even pump, the 0w30 will flow easily. Thicker is not "always better." It depends on the engine and the driving conditions. There are some engines for which a thicker oil--like 15w40 or even 20w50--is the best choice. But for most modern engines, a 0w30, 5w30, or 10w30 is the ideal choice. And even 5w20 is making a remarkably good showing in applications where just a few years ago no one would have dreamed of using an oil of that grade, e.g., a fully loaded Ford F350 with a V10 engine.
 
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quote:
A 0w30 oil is one that "behaves" in cold weather like a 0 weight oil
G-Man, you know better. Is oil thicker or thinner when cold? Thicker. A SAE Zero would be THINNER. [Razz]
 
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Oil doesn't behave like anything. The labelled weight is a SAE J300 spec. Look at the oil; its thicker when cold and thins out as it warms out. The bottle numbers are a big misnomer. Read your owners manual for recommended weights. The thicker is better argument isn't holding all that well anymore. Just take a look at all the excellent 20wt UOAs and the number of automfgs switching to thin oils.
 
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quote:
Originally posted by Audi Junkie:
quote:
A 0w30 oil is one that "behaves" in cold weather like a 0 weight oil
G-Man, you know better. Is oil thicker or thinner when cold? Thicker. A SAE Zero would be THINNER. [Razz]

Thinner than what? A 0wt oil and a 0w30 SHOULD be the same "thickness" (within the J300 guidelines) at -35. Once the temps start getting up to 0, you'll start seeing the 0w30 being "thicker," but you'd have to get above freezing before it would be much thicker.
 
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quote:
Originally posted by unDummy: Oil doesn't behave like anything. The labelled weight is a SAE J300 spec. Look at the oil; its thicker when cold and thins out as it warms out. The bottle numbers are a big misnomer.
[LOL!]
 
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39,805
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quote:
what do these numbers mean?
Look at this chart:  - Look at the scale on the left ..and index your view to include the SAE "low" spec of your oil. For example "10" falls (by eyeball) between 20 and 30 on the 40C cST scale. Now go to the high temp 100C scale. 30 weight appears to fall between 10 and 13. So an oil that is within the 10 range on the low temp scale ..and is within the 30 range on the high temp scale ..would be a 10-30. I'm assuming that a 0-40 would be below the 5 range on the low temp scale while being within the 40 on the high temp scale. In short a 10-30 oil meets AT LEAST the maximum requirements of a 10 weight oil at the lower temp and AT LEAST the minimum requirements of a 30 weight at the higher temp. [ May 27, 2004, 07:11 AM: Message edited by: Gary Allan ]
 
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Let's also bear in mind that the number before the W refers to the oil's performance at low temperatures. 80 fahrenheit degrees isn't a low temperature. German Castrol in 0W30 may very well not be the slightest bit thinner than your average 10W30 when you're at 80 degrees fahrenheit.
 
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G-man, whats so funny? TomJones, I'm under the impression that German Castrol 0w30 is thicker than some(see GCs synth competitors) 5w30s and 10w30s when hot. Look at GaryAllans chart and compare to the TallPall's SAE J300 spec: 0w-25w are NOT tested above 100c or at 40c on the spec; Cross out those parts of the chart when comparing motor oils. SAE 20-60 are not tested below 100c on the SAE spec. Cross out those parts of the chart. So, how do you compare the "W" with the "non-W" SAE weights. You don't! Because at 100c, the "W" specs have no max. The mins at 100c are the same for 15w, 20w, & 20. The mins at 100c are the same for 25w and 30. SAE J300 explains oil grades. I don't care for the above all inclusive grade chart. This is better: http://www.ethyl.com/products/la/handbook/Viscosity.pdf The bottle numbers are a misnomer. The 1st number (#W) should never be compared to the 2nd number on a multiweight oil. And the 1st number on a multiweight oil should never be compared to the only number on a straight SAE grade. You can buy almost any multiweight. And you can buy almost any straight SAE30-SAE60 oil. But, when was the last time you saw a straight SAE 0w - 25w oil? Also, it is possible for a SAE30 to flow like a 0w, 5w, 10w, 15w, 20w, or even a 25w oil. It as simple as the oil blender saving money, or not bother testing(or accurately blending) the oil for the multiweight label. Also, Kickster, the hotter the OIL gets, the thinner its gets(until it sludges up). With an oil cooler and thermostat, my ENGINE can go from cool to very hot with minimal change in oil viscosity. Read your owners manual for choices. If not happy with them, use the outside weather, location, engine condition, and some common sense when choosing a straight or multiweight oil. A little more info on that VW(year type size hp......) would help in making that choice. There is NO best unless proven with UOAs. Good luck in your decision!
 
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Now I'm not arguing with you ..but after reading what you posted ...I don't quite got a grip on what you're trying to say here..
quote:
0w-25w are NOT tested above 100c or at 40c on the spec
I'll assume that you mean 0 thru 25w ..and can I assume you mean "straight" weight?
quote:
Cross out those parts of the chart.
Even when comparing 0 thru 25W oils?
quote:

quote:
SAE 20-60 are not tested below 100c on the SAE spec
Again I'll assume that you mean stright 10 through 60 weight oils are not tested below 100C.
quote:
Cross out those parts of the chart.
Ditto??
quote:
So, how do you compare the "W" with the "non-W" SAE weights. You don't! Because at 100c, the "W" specs have no max.
I need something more than this. Like "take a xxxW ..see how it is jjjkkkll? Now look at non-W...."
quote:
The bottle numbers are a misnomer. The 1st number (#W) should never be compared to the 2nd number on a multiweight oil. And the 1st number on a multiweight oil should never be compared to the only number on a straight SAE grade.
I don't completely agree. For example a 10w-30 is typically a 20 weight oil. It meets the maximum requirements of a 10 weight oil. IF it has a W (typically all do ..but it is not a mandate) it is a winter grade. It meets the minimum requirements of a 30 weight. So ..I sorta agree ..but your assertion is too one dimensional ..at least in explanation.
quote:
But, when was the last time you saw a straight SAE 0w - 25w oil?
I believe that it's readily available ..but I doubt unless you're into bulk purchases ..that anyone here has seen it. My old plant had 55 gal drums of 10w Delo 400. I accepted the offer to take their remaining stocks of it since the plant was closing and no one wanted it. From their site:
quote:
Chevron Delo® 400 SAE 10W-30, 10W, 20, 30, 40, 50 Chevron Delo 400 heavy duty motor oils are exceptional, super premium quality "universal" engine oils which exceed industry and engine manufacturers' performance requirements.
I need you to bracket and qualify your statements a little. Sorry ...I'm challenged [Big Grin] [ May 27, 2004, 11:12 AM: Message edited by: Gary Allan ]
 
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A 0W-25W oil is not a multi-viscosity motor oil designation even though it depicts the same minimum ratings @ 100C as a 0W-30 on the Infineum chart. A multi-viscosity motor oil, 0W-30, is measured at the higher temperature levels of 40C & 100C, where a 0W-25W rating, if it existed, has no rating at the higher temperatures. [ May 27, 2004, 11:35 AM: Message edited by: Blue99 ]
 
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39,805
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quote:
In theory, if it was available, would a quart bottle labeled 20W-20 contain the same viscosity oil as one labeled SAE 20?
You must be young. It was readily available at one time. I think that the answer is something like "a square is a rectangle ..but a rectangle is not a square". A 20w-20 (allegedly) MUST fill requirements of 20 weight at both temps ..and one could assume that so would the straight as well ..but do they have the same(as in identical) Brookfield viscosity at whatever temp the test standard employs (is that what you're asking?)???
 
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quote:
Where did you hear this?
It may infact be out of vogue due to our evolutions in oil over the last 25 years. That is, in 1975 (for example) a 10W -30 WAS a 20 weight oil that bumped the qualifications of the 10 and the 30. Initially there were two weights of multivisc oil ..20 and 30. A 10-30 was a 20 weight ..a 10-40 was a 30 weight. They each met the min and max requirements of the polarized assigned notations. The "W" implies "WINTER" grade. Since you're also apparently young ..you've also never seen a oil that was a multivisc that DIDN'T have a "W" in it. ..but.. I'm always up for refresher courses here. Did you have any trouble with anything else I posted?? "One swallow does not the summer make." [ May 27, 2004, 01:13 PM: Message edited by: Gary Allan ]
 
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Gary My take on this one
quote:
0w-25w are NOT tested above 100c or at 40c on the spec
is that the API chart I posted the link to indicates that the "w" grades are tested for cold cranking and cold pumping, but must be tested for 100C performance in that the API chart gives a minimum 100C performance requirement. I also agree with you that a multigrade being simply a modified straight weight is probably outdated as unDummy's link shows that base oils come in a multitude of viscosity weights. Good thing too. I would rather my oil be built off a certain viscosity than a mixture of two different viscosities (a dumbell molecule distribution). I find it interesting that the 10w40 has the thicker base than 10w30 and it makes sense since you would want to minimize the VII input on the wider spread. But that an 0w40 would have a thicker base oil than 10w30 does not make sense. If it does then it would have to be because the 0w40 is synthetic. The stuff Redline told me on the 5w oils makes sense because you hear a lot on this site about 5w30s collapsing into 5w20s. I have heard about 20w20 and they used to have an oil titled 10w-20w-30. I was a pump jockey in the mid-70s when the typical recommendation was 10w40 summer/10w30 winter.
 
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The first number indicates an oil's cold pumpability. For eg. a 0 must be able to pump at -35C, a 5W at -30C and so on. The second number relates to an oil's viscosity at 100C. A 50 will be thicker than a 40, etc. based on the above chart.
 
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here's what I don't understand, some oil's viscosity specs, from the manufacturer:
code:
Viscosity in cSt
oil      sae weight  [email protected]    [email protected]
mobil-1    0w30      10.3         56
mobil-1    5w30      10.0         56
mobil-1   10w30      10.0         60
mobil-1    0w40      14.3         80
delvac    10w30      11.5         74
delvac    15w40      15.5        117
valvoline  5w20       8.5         48   (dino)
valvoline  5w30      10.7         63   (dino)
valvoline 10w30      10.5         71   (dino)

for ?w-20 or ?w-30 oils, ? should be >= SAE 20 according to the chart. For the 40C viscosity in cSt scale, the bottom of the SAE 20 region is under 40 cSt, and for all the specs given by manufacterers the lowest viscosity at 40C I've seen is 48cSt. So why aren't all oil's labeled 20w-20 or 20w-30?
 
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1 FMF: Your chart (based on 40C viscosity, which is not really cold temp, but) does support the assertion that 0w40's base oil is as thick as or thicker than a 10w30. Wow, look a the 40C jump from 10w30 up to 15w. Not sure I understand about the "for ?w-20 or ?w-30 oils, ? should be >= SAE 20 according to the chart," but it probably is that you need to look at the cold temp properties/viscosities (not available) rather than the luke warm temp viscosities.
 
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my point is only this: if a 5w-30 oil is supposed to behave like a SAE 5w oil in winter (when cold), then how come none of the 5w-20 or 5w-30 oils have a 40C viscosity rating of 20cSt or less according to the Grade Systems viscosity chart posted above? And the same for 10w-30 oils, they should have 35cSt or less according to the chart. I understand 40C = 104F, not necessarily cold. I guess the SAE winter numbers do not correspond to viscosity at 40C, so then what is the SAE winter number based on? Seems very arbitrary to me [I dont know]
 
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The cold temp for first number (5w-30) is tested at 0 degrees f. The 40c (100f) is only a point picked between 0 and 100c (212f) to get a vis number from. The ccs numbers such as 10.0 is how many seconds it takes for the fluid to pass thru a 6 mm hole in a funnel type device at a specified temperature. We have some at work. They are 50 mm diamter x 50 mm deep.
 
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