Does visc @ 40*C determine 5W, 10W etc?

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Does the viscosity @ 40 Celsius determine an oil rating of 0W, 5W, 10W etc? Here are some oil specs @ 40C: Mobil1 0W-40: 80.3 cSt RedLine 5W-40: 94 cSt Amsoil 10W-40: 79.2 cSt From the above, the Amsoil should flow the best at lower temperatures. Why is it a 10W and the thicker Redline a 5W? Would the Mobil1 or RedLine flow better than Amsoil at 10C? 0C?
 
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To add to Alex's question, if you compare the Cold cranking and Cold pumping numbers from the M1 data sheet Mobil1 data sheet does that mean the the 0W40 will not flow/crank as well as the 5 and 10W30 M1 oils? [ February 09, 2003, 11:52 PM: Message edited by: Quick_lude ]
 
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quote:
Originally posted by Ferrari: Does the viscosity @ 40 Celsius determine an oil rating of 0W, 5W, 10W etc?
No. The SAE J-300 spec gives the viscosity range for each grade, 0w through 25w, and 20 through 60. The low temp viscosity is based on CCS Cranking viscosity at various low temps, from -35*C for 0w to -10*C for 25w, and MRV pumping viscosity at various low temps, from -40*C for 0w to -15*C for 25w.
 
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quote:
Originally posted by Quick_lude: To add to Alex's question, if you compare the Cold cranking and Cold pumping numbers from the M1 data sheet does that mean the the 0W40 will not flow/crank as well as the 5 and 10W30 M1 oils?
Why can't you guys include a link without making the name of the link the entire URL? It's really easy to do, and it won't skew the screen. [Mad] [ February 10, 2003, 05:24 AM: Message edited by: Patman ]
 
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quote:
Originally posted by Quick_lude: To add to Alex's question, if you compare the Cold cranking and Cold pumping numbers from the M1 data sheet, does that mean the the 0W40 will not flow/crank as well as the 5 and 10W30 M1 oils?
No, it doesn't mean that at all. If you look closely, you'll see that the cold viscosity numbers for the 0w30 and 0w40 oils are measured at -35*C, the 5w30 is measured at -30*C, and the 10w30 is measured at -25*C. You can't compare the numbers directly because they aren't all at the same temp.
 
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Do'h! [Duh!] You're right about the temps, how did I not see that.. So to conclude the 0w40 should flow/crank just as well as the 5w and 10w weights correct? Fixed the link sorry. [Smile] [ February 09, 2003, 11:53 PM: Message edited by: Quick_lude ]
 
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Originally posted by Quick_lude: Do'h! [Duh!] You're right about the temps, how did I not see that.. So to conclude the 0w40 should flow/crank just as well as the 5w and 10w weights correct? I'd fix the link but I can't edit the post, sorry. [Smile]
No, to conclude, (if we're talking about Mobil 1) the 0w40 should flow BETTER than either the 5w30 or 10w30 at low temps, but it won't flow quite as good as the 0w30.
 
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Ferrari, remember that 40C is like 120F...not exactly cold. So no, CCS number's determine the Cold Cranking ability. ie. viscosity when cold eg. -20, -25C etc. depending on the grade and determined by API. eg. API doesn't ask a 20w-50 to crank at -25C, so you won't see a number at this temp.. Although, I was reading up on things and w.r.t. VI, it is apparently determined by the CCS #'s at 40 and 100C. Wonder what the formula is?
 
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