First, it's NOT a '50weight' oil. If one uses only one number and does not specify the temp, you're talking about the viscosity at 40dC, which is the first number in a multirange oil. Your 15W-50 is a high-viscosity-index 15W oil.quote:
Originally posted by StiMan:
...Doesnt it say viscocity is about 200 to 250 for a 50weight oil?
SAE J300 defines SAE viscosity. Last time I read it it didn't not give any requirements for 40Cquote:
Originally posted by Jeffrey Behr:
Therefore SAE 15-vis.'s range MUST start higher than the top of SAE-10's 50.6 and lower than the bottom of SAE-20's 61.2. That's how I came up with my range of 51 - 61.
pruizgarcia, if an oil has a centistoke viscosity at 40dC of 'over 100', it would be labeled AT LEAST an SAE 30. Look at the chart again.
I really wish they would simply publish the viscosity at -20C, 0C, and 20C, this way we could see what the viscosity of these oils are under actual temperatures many of us might see. There aren't too many places in North America that you're gonna see 40C temperatures, and even in the rare places where you do, cold starting is obviously not going to be much of a problem!quote:
Originally posted by heyjay:
I've often wondered why they even list the kinematic viscosity at 40 C? What use is it to you?
Yes, I realize that, and I'm simply saying that if they tested the viscosity of the oils at those temps instead of at just 40 and 100, it would give people a better idea of how the oil performs when in service. I think the 100C viscosity is the perfect hot temperature viscosity to give us, since most cars will have their oil temp relatively close to this point. But having a good idea of the viscosity of an oil when it's at a cooler temperature than 40C would give us a better idea of how to compare them to each other. Just another data point in other words, in addition to the all important cold cranking numbers.quote:
Originally posted by heyjay:
Sorry Patman I was refering to the kinematic viscosity of the oil at "operating" temp of 100 C and HTHS of 150 C. Not the ambient temp.
I really wish they would simply publish the viscosity at -20C, 0C, and 20C, this way we could see what the viscosity of these oils are under actual temperatures many of us might see. There aren't too many places in North America that you're gonna see 40C temperatures, and even in the rare places where you do, cold starting is obviously not going to be much of a problem!quote:
Originally posted by Patman:
So what you're trying to find are MRV values?quote:
Originally posted by Patman:
Yes, I realize that, and I'm simply saying that if they tested the viscosity of the oils at those temps instead of at just 40 and 100, it would give people a better idea of how the oil performs when in service. I think the 100C viscosity is the perfect hot temperature viscosity to give us, since most cars will have their oil temp relatively close to this point. But having a good idea of the viscosity of an oil when it's at a cooler temperature than 40C would give us a better idea of how to compare them to each other. Just another data point in other words, in addition to the all important cold cranking numbers.quote:
Originally posted by heyjay:
Sorry Patman I was refering to the kinematic viscosity of the oil at "operating" temp of 100 C and HTHS of 150 C. Not the ambient temp.
Most definitely! While we don't get the extreme cold like you guys in Northern Ontario get, it has definitely been a very cold January here, this morning getting down to -23C for example, and many mornings of -20 these last few weeks. I do run 0w30 German Castrol though, plus plug in a block heater on a timer (set to come on 4.5 hours before I leave) so I'm hopeful my oil analysis results from this interval will show relatively reasonable wear. I am lucky to be able to park in underground parking at work, where the coldest it's gotten down there so far has been 40F.quote:
There is a distinct difference in test procedures for testing oils at "normal" temps (Kinematic ASTM D445) and for testing their ability to pump at very cold temps (MRV using ASTM D4684). Places like Missisauga and St. Catherines have been cold enough this winter to worry about the cold MRV values.