10W-40 in the winter?

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233
Location
Pullman WA
I know that 10W-40 and 10W-30 are supposed to pour the same (10W) but I noticed from a couple of posts here that people have said that 10W-40 is still a thicker viscosity than 10W-30 in cold temps, is this true? I have been using 10W-40 in a 1987 Mazda B2000 with a 2.0 liter, the owners manual recommends it. Should I switch to a 10W-30 this winter? The temps here rarely get below zero degrees, but we do get lots of snow. Thanks.
 

Patman

Staff member
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22,012
Location
Guelph, Ontario
Even though they are both 10w, often times the 10w40 does not have as good cold cranking numbers as the 10w30 from the same brand. This is because the 10w40 might just barely qualify for 10w status while the 10w30 version might be well under the limit. That's why it helps when oil companies give us the exact specs for the cold cranking numbers (unlike Castrol which gives non specific numbers for that data)
 
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2,569
Location
College Dorm...
Yes, although they are both technically 10w oils, a 10w-40 is much thicker in cold conditions compared to a 10w-30. For example, lets take a look at the viscosity of Chevron Supreme (at 40C): 10w-30: 73.5cSt 10w-40: 104cSt If you have been using a 10w-40 and have had no problems, I see no reason to switch. Otherwise, a 10w-30 would be better in the cold. BTW, I personally believe this is done to aleviate a good deal of the shearing problems inherent with wide-spread mineral oils. Less spread = less need to VII's.
 
Messages
2,058
Location
Sequim, WA
You can't compare the cold viscosity characteristics of oils by looking at the 40C viscosity. That's 104F, hardly cold. Of course a 40 weight is going to be thicker. You have to look at the cold cranking data, if you can find it. Here's a couple of examples: Chevron Supreme 10W-30: [email protected] Chevron Supreme 10W-40: [email protected] In this case the 10W-40 is a bit thicker. Mobil Drive Clean 10W-30: [email protected] Mobil Drive Clean 10W-40: [email protected] Mobil DC Plus 10W-30: [email protected] Mobil DC Plus 10W-40: [email protected] In the case of the Mobil oils, the 10W-40 offers "better" cold performance. Ed
 

MustangGT

Thread starter
Messages
233
Location
Pullman WA
Thanks for the help, I have (4) quarts of chevron 10W-40 and I was debating whether to use them or not in my next oil change, or to try Pennzoil high mileage 10W-30 instead. Maybe I'll just stick with the chevron. Thanks
 
Messages
1,412
Location
Falls Church VA
If you are using synthetic, you probably won't notice much difference. Heck, folks used AMSOIL in the cold country for many years when the 10W-40 was the only one available. CCS AMSOIL 10W-40 4500 @-25C 10W-30 3444 @-25
 
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47,824
Location
Everson WA - Pacific NW USA
I use Amsoil 10W-40 in one Volvo and 15W-40 in another year round on this side of the mountains in Lynden. Yeah Pullman gets cold, but not that cold. 10W-40 will be fine, synthetic much better in cold, no doubt about it.
 
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2,569
Location
College Dorm...
quote:
Originally posted by edhackett: You can't compare the cold viscosity characteristics of oils by looking at the 40C viscosity. That's 104F, hardly cold. Of course a 40 weight is going to be thicker.
Ed, Thanks for pointing out my obvious mistake there...I should know better (I'm embarrassed!). Oh well, I'm entitled one stupid mistake... [ October 22, 2003, 09:28 PM: Message edited by: Jelly ]
 
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