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#7556 - 09/26/02 04:42 AM What does the "W" stand for?
Dr. T Offline


Registered: 05/28/02
Posts: 2480
Probably a stupid question (and hopefully easily answered), but I just read the following quote on another website:

"The W means the oil meets specifications for viscosity at 0 F and is therefore suitable for Winter use"

But, what are the viscosity specs at 0 F that make an oil suitable for an SAE "W" rating?

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#7557 - 09/26/02 05:13 AM Re: What does the "W" stand for?
Brad Offline


Registered: 07/13/02
Posts: 116
Loc: Cincinnati, OH
Do you mean like the "W" in 5w-30? In that case the "W" means weight.

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#7558 - 09/26/02 05:33 AM Re: What does the "W" stand for?
pgtr Offline


Registered: 09/24/02
Posts: 263
Loc: tx
No, the "W" used in 5W30 for example does not mean weight. I always consider it means "Winter" or winter rated or cold weather related or whatever.

It means pretty much what your quote says which is to say it's OK for winter use. I can't answer your question about what exact viscosity it must be at 0 to get the "W" rating but I don't recall seeing motor oils above 20 w/ a "W" rating. So I'll guess anything at 20 or below in viscosity at 0 is it. BTW is it 0 F or 0 C?

I think there are specific test(s) it must pass to meet the "W" rating. FOr example you can buy an SAE 20 or an SAE 20W - the difference? Not sure but I'm guessing one passed the winter pour tests and the other either didn't or the manufacturer didnt' bother to test them or bother to include the W designation.

To be loosey goosey the 'general' wisdom is that 20 and below is generally considered adequate for winter usage and above 20 isn't as far as motor oils go.

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#7559 - 09/26/02 05:35 AM Re: What does the "W" stand for?
bretfraz Offline


Registered: 06/21/02
Posts: 2756
Loc: CarMax
Ummm..... actually "W" stands for "winter" meaning the oil meets the SAE spec for low temp pumpability.

Sez so right here:
_______________________________________
Oil weight, or viscosity, refers to how thick or thin the oil is. The temperature requirements set for oil by the Society of Automotive Engineers (SAE) is 0 degrees F (low) and 210 degrees F (high).

Oils meeting the SAE's low temperature requirements have a "W" after the viscosity rating (example: 10W), and oils that meet the high ratings have no letter (example SAE 30). An oil is rated for viscosity by heating it to a specified temperature, and then allowing it to flow out of a specifically sized hole. Its viscosity rating is determined by the length of time it takes to flow out of the hole. If it flows quickly, it gets a low rating. If it flows slowly, it gets a high rating.

Engines need oil that is thin enough for cold starts, and thick enough when the engine is hot. Since oil gets thinner when heated, and thicker when cooled, most of us use what are called multi-grade, or multi-viscosity oils. These oils meet SAE specifications for the low temperature requirements of a light oil and the high temperature requirements of a heavy oil. You will hear them referred to as multi-viscosity, all-season and all-weather oils. An example is a 10W-30 which is commonly found in stores. When choosing oil, always follow the manufacturer's recommendation.

_______________________________________
Sorry, Brad.

[ September 30, 2002, 01:54 PM: Message edited by: BOBISTHEOILGUY ]

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#7560 - 09/26/02 07:03 AM Re: What does the "W" stand for?
sprintman Offline


Registered: 05/27/02
Posts: 11006
Loc: Canberra ACT Australia
WINTER

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#7561 - 09/26/02 11:15 PM Re: What does the "W" stand for?
Anonymous
Unregistered


Here is the test for oil viscosity, both for viscoisities with "W" and without.

Note, for example, that 20W oil meets a completely different test than 20 wt.

http://www.chevron.com/prodserv/NewOronite/library/li_viscosity_motoroil.htm

Ken

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#7562 - 09/26/02 11:19 PM Re: What does the "W" stand for?
Dominic Offline


Registered: 07/04/02
Posts: 1779
Loc: Alabama
a 5W 30 pumpably performs like an SAE5 when cold, and an SAE30 when hot. This does not mean it THICKENS when it warms, only that it retains its viscosity enough to remain in the SAE30 grade when hot.

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#7563 - 09/27/02 06:04 AM Re: What does the "W" stand for?
Anonymous
Unregistered


quote:
Originally posted by Dominic:
a 5W 30 pumpably performs like an SAE5 when cold, and an SAE30 when hot. This does not mean it THICKENS when it warms, only that it retains its viscosity enough to remain in the SAE30 grade when hot.

No.

There is no SAE 5 wt. 5W-30 meets the 5W viscosity test (which is a cold test) and it meets the 30 wt. viscosity test (which is a hot test).

Ken

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#7564 - 09/27/02 06:50 AM Re: What does the "W" stand for?
jjbula Offline


Registered: 07/04/02
Posts: 479
Loc: Montgomery, AL
quote:
Originally posted by Dr. T:

"The W means the oil meets specifications for viscosity at 0 F and is therefore suitable for Winter use"

But, what are the viscosity specs at 0 F that make an oil suitable for an SAE "W" rating?

Not to knock the good information you have received already, just to add how I use it...

The SAE specs for pumpability and thickness (viscosity) of cold oil are graduated for the type. 0w or 5w or 10w. IMHO the standard is a minimum and a good oil will be much, much better. Some believe (as do I) that better than standard oil flow during a cold start will decrease engine wear. It also offsets any oil thickening before the next drain.

Look at synthetic oil specs vs. dino specs. The synthetic will always have better cold flow properties for the same "winter" number (0w 5w). IMHO that is the most useful advantage of a synthetic for the average family car/truck.

0F and -20F seem to be popular dividing lines

I use 5w for 0F and would 0w for -20F. Owner manuals may use different cut-offs but are based on Dino oil.

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#7565 - 09/27/02 12:57 PM Re: What does the "W" stand for?
Patman Offline



Registered: 05/27/02
Posts: 19281
Loc: Oakville, Ontario
I still don't understand how most 20w50 oils could possibly be rated as "winter oils"

I sure wouldn't run 20w50 Castrol GTX in the winter with it's terrible -21C pour point. That means this oil wouldn't be much good below about -10C, which is the normal overnight low here in Toronto for most of the winter.

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#7566 - 09/27/02 04:43 PM Re: What does the "W" stand for?
ZR2RANDO Offline


Registered: 06/10/02
Posts: 885
Loc: North Carolina
Last time I checked the Havoline/Chevron pages showed the 20w/50 oil had a pour point of -31F which would put the minimum pump point at somewhere near -20F. It may be that cold up in Canada and therefore would not be a good oil for use up there, but down south here in NC we don't see that temp even in the worst of winter. That wt of oil works fine in this type climate, we usually are more concerned with handling the summer heat than with the winter cold. Winter for me usually bottoms out at about 15F at it worst, and down here we usually shut the place down if it snows,,,just kidding, but really, any oil that may be great up north is not neccessarily very good down south,
20w/50 just means that you have a sae20 oil when cold that thins out as much as a 50wt oil would when hot (I think the reference cold is 0C and the hot is 100C)
It's sorta like the old saying, different strokes for different folks, one man's trash, another man's gold kinda thing.
see y'all
ARE YA READY FOR SOME FOOTBALL??????

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#7567 - 09/27/02 04:56 PM Re: What does the "W" stand for?
widman Offline


Registered: 05/27/02
Posts: 3061
Loc: Bolivia
20w50 isn't for everyone. I recommend it for a lot of trucks and busses that are getting up in miles and cover the part of the country where temperatures run from -8C to +58 C with occasional trips into the -15 C areas. Plenty of safety there. My 91 Tracker and 88 BMW specify it for those temps as the preferred oil (pre-CAFE).

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#7568 - 09/29/02 03:49 AM Re: What does the "W" stand for?
Dr. T Offline


Registered: 05/28/02
Posts: 2480
On many web sites, the old stats for Castrol GTX 20-50 pour point is -15 F. This is -26 C. Remember, pour point is usually measure in F and CCSt is referenced from degrees C.

So from what I can gather, the "W" refers to an oil's pumpability with respect to temperature. This means that the CCSt is what we're talking about here and this is always referenced from a higher number than ultimate pour point. Which means a grade of 5, 10, or 15 is referenced from it's crankablility at a certain temp. (and I'm guessing this is what determines the oil grade chart) over ultimate pour point. eg. M-1 15-50 pours at -45 F, but even at -30 F it may by impossible to crank over (just as the GTX) even though it has a much lower pour point. Ultimately though, such an oil will perform better lower temps and give an added safety margin...This is why my owner's manual states (conventional oils) to use 15-50 down to -20 C (-4F)...and it's acceptable if it goes slightly below this temp. for short periods...

I just completed a freezer test of M-1 SS. Freezer went down to -28 C (-18 F). Sure the oils was still able to move, but it was thick...we'll see this winter...like Patman says, it goes down to (if I can remember accurately from last winter) about -18 C (0 F) at the max...so if the alternator can crank through it...it will pour....as far as it getting to all the parts sooner? Who knows...if it can pump, it should reach all the components the same as any other viscosity (5 or 10W)...

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#7569 - 09/29/02 08:26 AM Re: What does the "W" stand for?
Jay Offline


Registered: 07/16/02
Posts: 1600
Loc: Arroyo Grande, CA
quote:
Originally posted by Ken:

No.

There is no SAE 5 wt. 5W-30 meets the 5W viscosity test (which is a cold test) and it meets the 30 wt. viscosity test (which is a hot test).

Ken[/QB]

Thanks for the Chevron link you posted earlier. I believe there is an SAE 5 and SAE 10 although the Chevron chart doesn't show it.

http://www.bobistheoilguy.com/visc.html

Neo sells a 0w-5 motor oil.

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#7570 - 09/29/02 08:31 AM Re: What does the "W" stand for?
Jay Offline


Registered: 07/16/02
Posts: 1600
Loc: Arroyo Grande, CA
Ahhh, never mind. And why can't I edit my posts? Administrators?!!

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