COLD WEATHER STARTS: AGENTS OF DOOM
The pour point of an oil is 5 degrees F above the point at which a chilled oil shows no movement at the surface for 5 seconds when inclined. That's tech-talk which basically means that the pour point of an oil is the point at which it ceases to be "pourable". This measurement is especially important for oils used in cold climates.
A borderline pumping temperature is given by some manufacturers. This is the lowest temperature at which the oil will pump and maintain adequate oil pressure within an engine. This is not given by a lot of the manufacturers, but can be anywhere from 5 to 15 or 20 degrees F above the pour point. So, the lower the pour point the better.
For cold weather operation, most vehicles should be running a 5w30 or 10w30 motor oil. Most 5w30 petroleum oils have pour points in the range of -30 to -40 degrees F. That means that their borderline pumping temperature is, between -35 and -15 degrees F when they come out of the bottle. In most cases, closer to the warmer end of the scale.
In a cold climate where every day is 0 degrees or lower, the pour point depressant additives in a petroleum oil are used up quickly. As these additives are used up, the pour point (and borderline pumping temperature) of the oil rises. In addition, after the engine heats up the oil is subjected to high temperature conditions that burn off the lighter molecules in a petroleum oil, causing it to thicken.
So, if you're running a petroleum 5w30, expect decent cold weather starts when the oil comes out of the bottle. But, after a thousand miles or so, don't expect to go out and start your car at -10 degrees and have it purr like a kitten. It's going to spit and sputter and kick and scream for a few minutes.
Why do you think that is? It's not getting any oil up into the engine. It's like trying to suck molasses through a tiny straw in an Alaskan January. There's literally nothing keeping the metal components in your engine from tearing each other apart. Every time you start your engine in conditions like this, your engine dies a little bit more. Your oil is dying, and it's taking your engine with it.
Synthetic oils, on the other hand, routinely have pour points around -50 degrees F or colder. Some have pour points as low as -60 to -70 degrees F. Granted, there are very few of us who will ever have to start our car at this temperature, but imagine how well these oils lubricate at -20, if it they still flow at -70. And, because synthetics don't need additives to maintain their low temperature fluidity (as we discussed earlier), they continue to flow at these extremely low temperatures for a much longer period of time.
Now, I know that some of you live in areas where you almost never see temperatures under freezing. For you folks, the pour point of your oil may be a little less important, but it still serves to prove a point about the protection differences between petroleum oils and synthetics.
[ October 09, 2002, 06:56 PM: Message edited by: BOBISTHEOILGUY ]
The pour point of an oil is 5 degrees F above the point at which a chilled oil shows no movement at the surface for 5 seconds when inclined. That's tech-talk which basically means that the pour point of an oil is the point at which it ceases to be "pourable". This measurement is especially important for oils used in cold climates.
A borderline pumping temperature is given by some manufacturers. This is the lowest temperature at which the oil will pump and maintain adequate oil pressure within an engine. This is not given by a lot of the manufacturers, but can be anywhere from 5 to 15 or 20 degrees F above the pour point. So, the lower the pour point the better.
For cold weather operation, most vehicles should be running a 5w30 or 10w30 motor oil. Most 5w30 petroleum oils have pour points in the range of -30 to -40 degrees F. That means that their borderline pumping temperature is, between -35 and -15 degrees F when they come out of the bottle. In most cases, closer to the warmer end of the scale.
In a cold climate where every day is 0 degrees or lower, the pour point depressant additives in a petroleum oil are used up quickly. As these additives are used up, the pour point (and borderline pumping temperature) of the oil rises. In addition, after the engine heats up the oil is subjected to high temperature conditions that burn off the lighter molecules in a petroleum oil, causing it to thicken.
So, if you're running a petroleum 5w30, expect decent cold weather starts when the oil comes out of the bottle. But, after a thousand miles or so, don't expect to go out and start your car at -10 degrees and have it purr like a kitten. It's going to spit and sputter and kick and scream for a few minutes.
Why do you think that is? It's not getting any oil up into the engine. It's like trying to suck molasses through a tiny straw in an Alaskan January. There's literally nothing keeping the metal components in your engine from tearing each other apart. Every time you start your engine in conditions like this, your engine dies a little bit more. Your oil is dying, and it's taking your engine with it.
Synthetic oils, on the other hand, routinely have pour points around -50 degrees F or colder. Some have pour points as low as -60 to -70 degrees F. Granted, there are very few of us who will ever have to start our car at this temperature, but imagine how well these oils lubricate at -20, if it they still flow at -70. And, because synthetics don't need additives to maintain their low temperature fluidity (as we discussed earlier), they continue to flow at these extremely low temperatures for a much longer period of time.
Now, I know that some of you live in areas where you almost never see temperatures under freezing. For you folks, the pour point of your oil may be a little less important, but it still serves to prove a point about the protection differences between petroleum oils and synthetics.
[ October 09, 2002, 06:56 PM: Message edited by: BOBISTHEOILGUY ]
