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#2437895 - 11/18/11 03:26 AM is 10w30 and 10w40 the same when cold
Dakota1820 Offline
formerly chevyboy14


Registered: 04/28/11
Posts: 3894
Loc: missouri usa
so basically my question is in the title. I noticed my car having start up noise and more cranking to start it with 10w40 yes I was warned and did it anyway. the best way to learn sometimes is the hard way. is 10w30 the same as 10w40 cold and is 5w30 a real big difference at all ? thanks all
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1998 Saturn sl2 -mobil super 5000 5w30


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#2437914 - 11/18/11 04:47 AM Re: is 10w30 and 10w40 the same when cold [Re: Dakota1820]
crinkles Offline


Registered: 05/28/07
Posts: 5484
Loc: Australia
the 10w-40 would be thicker. the 10w part relates to very cold temperatures, something like -30 deg c. at that low temperature, the cranking and pumping issues would be the same. above that temperature the 10w-40 is likely thicker for all temperatures.

the pumping spec for 5w and 10w is the same but 5w is tested at 5 deg c lower than the 10w. ow is tested at 10 deg c lower than 10w.

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#2437938 - 11/18/11 06:20 AM Re: is 10w30 and 10w40 the same when cold [Re: Dakota1820]
Robenstein Online   content


Registered: 12/23/09
Posts: 3158
Loc: Central IA
The first number in a multi grade oil is always the cold viscosity, so yes a 10w40 and 10w30 are going to have the same cold start up flow characteristics. However at operating temperature, the 10w40 will be thicker.

If you need good cold weather pumpability and a thicker oil, you can try Castol 0w30 syntec. Its blended on the thick side of a 30 weight but still has great cold weather flow.

You could also go with something like Rotella 5w40
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#2437961 - 11/18/11 06:57 AM Re: is 10w30 and 10w40 the same when cold [Re: Dakota1820]
JAG Offline


Registered: 10/23/05
Posts: 4523
Loc: Fredericksburg, VA
Generally no. For extreme cold temps., look at the MRV and CCS viscosities of the oils in question. For higher cold temps., use a viscosity calculator.

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#2438002 - 11/18/11 08:01 AM Re: is 10w30 and 10w40 the same when cold [Re: Dakota1820]
addyguy Offline


Registered: 09/08/05
Posts: 13427
Loc: Canada
The '10W' and '5W' values are a RANGE of cranking viscosities.

For 10W, it can't exceed 7,000centerpoise(cp) at -25 deg. C.

Within that range, different oils have different values, and, in general, a 10w-40 oil will have higher values than a 10W-30, b/c the over all oil is thicker.

For a fictional example, a 10W-30 oil may have a value of 5,600 at -25, while a 10W-40 will have a value of 6,600 at -25. Both are '10W' oils, but the 10W-40 is still thicker, and still has higher cranking values.
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#2438045 - 11/18/11 08:43 AM Re: is 10w30 and 10w40 the same when cold [Re: addyguy]
Drew99GT Online   happy


Registered: 10/11/02
Posts: 20662
Loc: Colorado Springs
Originally Posted By: addyguy
The '10W' and '5W' values are a RANGE of cranking viscosities.

For 10W, it can't exceed 7,000centerpoise(cp) at -25 deg. C.

Within that range, different oils have different values, and, in general, a 10w-40 oil will have higher values than a 10W-30, b/c the over all oil is thicker.

For a fictional example, a 10W-30 oil may have a value of 5,600 at -25, while a 10W-40 will have a value of 6,600 at -25. Both are '10W' oils, but the 10W-40 is still thicker, and still has higher cranking values.


approved In addition, the 10w SAE cold testing is done at -13F for CCS and -22F for MRV. I hope it's not that cold in Missouri currently! 10w-40 will have a thicker overall viscosity at all temps.

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#2438280 - 11/18/11 01:11 PM Re: is 10w30 and 10w40 the same when cold [Re: Dakota1820]
Dakota1820 Offline
formerly chevyboy14


Registered: 04/28/11
Posts: 3894
Loc: missouri usa
at 30 degrees my Saturn doesn't want 10w40. I guess 5w30 will be best
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#2438338 - 11/18/11 02:36 PM Re: is 10w30 and 10w40 the same when cold [Re: addyguy]
KCJeep Offline


Registered: 06/30/11
Posts: 4554
Loc: Mahzurrah!
Originally Posted By: addyguy
The '10W' and '5W' values are a RANGE of cranking viscosities.

For 10W, it can't exceed 7,000centerpoise(cp) at -25 deg. C.

Within that range, different oils have different values, and, in general, a 10w-40 oil will have higher values than a 10W-30, b/c the over all oil is thicker.

For a fictional example, a 10W-30 oil may have a value of 5,600 at -25, while a 10W-40 will have a value of 6,600 at -25. Both are '10W' oils, but the 10W-40 is still thicker, and still has higher cranking values.


approved Great answer!!!
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#2439016 - 11/19/11 10:56 AM Re: is 10w30 and 10w40 the same when cold [Re: Dakota1820]
Drew99GT Online   happy


Registered: 10/11/02
Posts: 20662
Loc: Colorado Springs
Originally Posted By: chevyboy14
at 30 degrees my Saturn doesn't want 10w40. I guess 5w30 will be best


Try a 5w-30 High Mileage oil. I think your Saturn will approve.

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#2439096 - 11/19/11 12:35 PM Re: is 10w30 and 10w40 the same when cold [Re: Dakota1820]
mechtech2 Offline


Registered: 09/05/06
Posts: 19479
Loc: Chicago Area
Lots of varied information above!
The 5 and 10 will be the same at 0 deg F. Pretty cold.
At operating temp [oil temp, not coolant], a 30 is a 30 - they are the same.
And intermediate temps? The 5 will be a bit thinner than the 10 up to full operating temps [200 f or so].

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#2439241 - 11/19/11 04:25 PM Re: is 10w30 and 10w40 the same when cold [Re: Dakota1820]
MrRPM Offline


Registered: 08/25/11
Posts: 437
Loc: Michigan
according to this http://www.bobistheoilguy.com/motor-oil-109/

a 10w-30 and a 10w-40 do NOT have the same cold temp thickness.
it appears that the 10w-40 will be thicker then the 10w-30 even though they are both 10w

weird
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#2439265 - 11/19/11 04:57 PM Re: is 10w30 and 10w40 the same when cold [Re: mechtech2]
Drew99GT Online   happy


Registered: 10/11/02
Posts: 20662
Loc: Colorado Springs
Originally Posted By: mechtech2

The 5 and 10 will be the same at 0 deg F. Pretty cold.


They might not be (and usually aren't). Look at the viscosity index, and the stated viscosities and plug them into a viscosity calculator.

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#2439700 - 11/20/11 09:02 AM Re: is 10w30 and 10w40 the same when cold [Re: mechtech2]
JAG Offline


Registered: 10/23/05
Posts: 4523
Loc: Fredericksburg, VA
Originally Posted By: mechtech2
The 5 and 10 will be the same at 0 deg F.

0 deg F has nothing to do with the SAE J300 that governs viscosity grades: http://widman.biz/English/Tables/J300.html

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#2439828 - 11/20/11 12:02 PM Re: is 10w30 and 10w40 the same when cold [Re: Dakota1820]
mechtech2 Offline


Registered: 09/05/06
Posts: 19479
Loc: Chicago Area
Oils are rated at 0 deg F, and 200 degF.
How could those temps not be relevant?

But back to the original poster's question:
There are of course differences by mfr - there is a slight RANGE for any viscosity designation. it makes no practical difference - the difference is tiny.
Even two of the SAME oils could show some difference, and have in testing!


Edited by mechtech2 (11/20/11 12:05 PM)

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#2439936 - 11/20/11 01:58 PM Re: is 10w30 and 10w40 the same when cold [Re: mechtech2]
JAG Offline


Registered: 10/23/05
Posts: 4523
Loc: Fredericksburg, VA
Originally Posted By: mechtech2
Oils are rated at 0 deg F, and 200 degF.
How could those temps not be relevant?

No they are not. Please read and understand the link I posted. This is a basic concept that nobody on this forum should mistake when posting. It makes the forum lose credibility.

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