Low temp. viscosity and pour point question...

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1,381
Location
Southeast Kentucky
I have been reading some older threads and I get the idea that low temp. (cold cranking) viscosity is a better indicator of cold weather behavior than pour point. Is that correct? I noticed that when comparing 5w30 oils, Pennzoil dino has a very low pour point of -42C but a Ccs of <[email protected] Chevron Supreme has a -36C pour point but the Ccs is [email protected] M1, a true synthetc 5w30 has a nice low [email protected] So is it the cold crank viscosity that's the true measure? Thanks.
 
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700
Location
USA
This is true. Pour point is just the temp that the oil shows some movement. Cold cranking is more important. Actually Mobil dino 5w-30 pours at -33f but yet has one of the best cold cranking at about 5500. I haven't looked at the Mobil web site for a few months, but this is what they used to be.
 
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3,216
Location
BC, Canada
In addition to the posted cold cranking and flow numbers, or if they are not listed, I like to use the viscosity index of an oil as an indication of its cold performance. For example, if an xxW30 has a VI of 180, it will likely pass an 0W flow and crank test.(= 0W30) If the oil has a VI of only 100 then it will likely be a straight weight. (=SAE 30) My rule of thumb is: For cold operation look for high VI numbers, for hot operation look for high flash point and low volatility and evaporation rates. Some engine oils have high VI and flash points, and low evaporation rates making them suitable for a broad temperature range. At a higher cost of course. I think that high VIs add little to the hot performance of a lubricant and are more of a cold flow indicator.
 

Jay

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1,607
Location
Idaho Falls, ID
quote:
Originally posted by Drew99GT: When looking at cold cranking viscosity, what are you looking for? The lower the number, the better the cold weather performance?
The lower the cold cranking and pumping viscosity the better. But look carefully at the temperature. The low temperature cranking and pumping viscosities are specified at a certain temperature. Don't try to compare viscosities at different temperatures.
 
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