Is there any "formula" for converting an oil's pour point to actual usage temperatures? For example, a poster on this site uses a 30 degree rule---he'll only use an oil down to a temperature that's 30 degrees or more higher than the pour point. So if the pour point is -30F, he'll use it down to 0 F. Is this a reasonable way to interpret and use pour points to select oils for expected temperatures? The reason I ask is because I like Rotella 15w-40 and it has a surprisingly low pour pount of -40 F so using the "30 degree rule" this would be good down to -10 F which would make it suitable for year 'round use. Any pour point guru's out there?
POUR POINTS
- Thread starter MADMIKE
- Start date
- Status
Hi Madmike,
I would not trust any such formula. Pour point measures the temperature at which the oil stops pouring under its own weight, that is, under low shear conditions. In the engine, oils are sucked and pumped, which is much higher shear conditions and does not correlate to pour point. This is why the specifications call for CCS and MRV viscosity measurements instead of pour point.
Imagine a bowl of Jell-O. If you tilt the bowl, the Jell-O will wobble and perhaps sag a bit, but it does not flow out of the bowl like a liquid. This lack of flow would suggest that the Jell-O is a solid that would not flow where needed. Now take a spoon and stir, and the Jell-O will move fairly freely under the force (shear) of your hand. Then take wide straw and suck the Jell-O - again the Jell-O will flow up the straw under this vacuum force, but it will not flow back into fill the hole you sucked out. In other words, applying a force to an apparent solid material can cause it to flow and pump, even though it cannot do so under its own weight. The reason is that the Jell-O has a weak crystalline structure that breaks easily under force (shear) and reverts back to a liquid like substance that can be easily moved.
A similar situation exists with motor oils since mineral oils have waxes that grow crystals under certain temperature conditions, causing a "freeze point" as opposed to a "pour point". The difference is that "pouring" stops when the viscosity rises to a point that the oil is just too stiff to flow, while "freezing" occurs when the crystal structure from the waxes "knits" the oil into a weak solid, sort of like Jell-O. Crystal growth in oils requires a very slow cool down to occur, often with a pause or soak period. The pour point test cools at a relatively fast rate that can "super cool" the fluid, that is, it whizzes (technical term
) right on past its freeze point and runs to its pour point, missing any freezing along the way.
The CCS test stirs the oil (applies shearing force) during the cool down and better simulates the shear rates of the oil pump than a simple pour point. The MRV test cools at a very slow rate with less shear and catches the effect of any freezing tendency.
Back in 1981 Quaker State had an oil that caused over 1,000 engines to seize due to these effects. The oil had a good pour point and CCS viscosity and could be readily sucked up and pumped by the oil pump when cold. However, their VI improver caused crystal growth under certain cooling conditions, turning the oil into a Jell-O like consistency in the pan. Then when the pump sucked the oil up from the reservoir in the pan, it created a hole and the oil was not able to flow back in and fill the hole. The pump then sucked air and the engines seized within minutes from oil starvation. This freezing phenomenon was prevalent and well documented in the Sioux Falls area where the temperatures during the failures cooled very slowly and paused for a while at about +10-15F. When simulated in the lab, the otherwise passing oil exhibited a freezing tendency. This temperature profile was referred to as the "Sioux Falls Cycle" and formed the basis of the cooling cycle used in the MRV test, which was then added to the J300 spec. QS owned up to the problem and paid the claims.
Tom
I would not trust any such formula. Pour point measures the temperature at which the oil stops pouring under its own weight, that is, under low shear conditions. In the engine, oils are sucked and pumped, which is much higher shear conditions and does not correlate to pour point. This is why the specifications call for CCS and MRV viscosity measurements instead of pour point.
Imagine a bowl of Jell-O. If you tilt the bowl, the Jell-O will wobble and perhaps sag a bit, but it does not flow out of the bowl like a liquid. This lack of flow would suggest that the Jell-O is a solid that would not flow where needed. Now take a spoon and stir, and the Jell-O will move fairly freely under the force (shear) of your hand. Then take wide straw and suck the Jell-O - again the Jell-O will flow up the straw under this vacuum force, but it will not flow back into fill the hole you sucked out. In other words, applying a force to an apparent solid material can cause it to flow and pump, even though it cannot do so under its own weight. The reason is that the Jell-O has a weak crystalline structure that breaks easily under force (shear) and reverts back to a liquid like substance that can be easily moved.
A similar situation exists with motor oils since mineral oils have waxes that grow crystals under certain temperature conditions, causing a "freeze point" as opposed to a "pour point". The difference is that "pouring" stops when the viscosity rises to a point that the oil is just too stiff to flow, while "freezing" occurs when the crystal structure from the waxes "knits" the oil into a weak solid, sort of like Jell-O. Crystal growth in oils requires a very slow cool down to occur, often with a pause or soak period. The pour point test cools at a relatively fast rate that can "super cool" the fluid, that is, it whizzes (technical term
The CCS test stirs the oil (applies shearing force) during the cool down and better simulates the shear rates of the oil pump than a simple pour point. The MRV test cools at a very slow rate with less shear and catches the effect of any freezing tendency.
Back in 1981 Quaker State had an oil that caused over 1,000 engines to seize due to these effects. The oil had a good pour point and CCS viscosity and could be readily sucked up and pumped by the oil pump when cold. However, their VI improver caused crystal growth under certain cooling conditions, turning the oil into a Jell-O like consistency in the pan. Then when the pump sucked the oil up from the reservoir in the pan, it created a hole and the oil was not able to flow back in and fill the hole. The pump then sucked air and the engines seized within minutes from oil starvation. This freezing phenomenon was prevalent and well documented in the Sioux Falls area where the temperatures during the failures cooled very slowly and paused for a while at about +10-15F. When simulated in the lab, the otherwise passing oil exhibited a freezing tendency. This temperature profile was referred to as the "Sioux Falls Cycle" and formed the basis of the cooling cycle used in the MRV test, which was then added to the J300 spec. QS owned up to the problem and paid the claims.
Tom
Back in 1981 Quaker State had an oil that caused over 1,000 engines to seize due to these effects. The oil had a good pour point and CCS viscosity and could be readily sucked up and pumped by the oil pump when cold. However, their VI improver caused crystal growth under certain cooling conditions, turning the oil into a Jell-O like consistency in the pan. Then when the pump sucked the oil up from the reservoir in the pan, it created a hole and the oil was not able to flow back in and fill the hole. The pump then sucked air and the engines seized within minutes from oil starvation. This freezing phenomenon was prevalent and well documented in the Sioux Falls area where the temperatures during the failures cooled very slowly and paused for a while at about +10-15F. When simulated in the lab, the otherwise passing oil exhibited a freezing tendency. This temperature profile was referred to as the "Sioux Falls Cycle" and formed the basis of the cooling cycle used in the MRV test, which was then added to the J300 spec. QS owned up to the problem and paid the claims.
when the Q flows the motor blows
when the Q flows the motor blows
Good stuff Tom!
MRV and CCS are the numbers to look at. For example, Rotella 5w-40 has a better pour point than 5w-30 dino it pumps 39,000 Cp I believe where as an average dino 5w-30 with a weaker pour point pumps about 20,000 Cp. The limit is 60,000 at -35C for 5w.
MRV and CCS are the numbers to look at. For example, Rotella 5w-40 has a better pour point than 5w-30 dino it pumps 39,000 Cp I believe where as an average dino 5w-30 with a weaker pour point pumps about 20,000 Cp. The limit is 60,000 at -35C for 5w.
Great Post, Tom!
While I fully accept it as a fact that Group II mineral oils will form wax in sub-zero F temperatures, I'm hazy about where it is coming from.
The base oils have gone thru either a isomerization process or de-waxing process to convert/remove the wax.
Does the cold temperatures cause some paraffinic hydrocarbon chains to reform into wax formations?
While I fully accept it as a fact that Group II mineral oils will form wax in sub-zero F temperatures, I'm hazy about where it is coming from.
The base oils have gone thru either a isomerization process or de-waxing process to convert/remove the wax.
Does the cold temperatures cause some paraffinic hydrocarbon chains to reform into wax formations?
Hi Blue,
The waxes were present in the starting crude oil. The relatively mild hydroprocessing used in Group II refining does not remove all of the waxes. Neither does the hydrocracking in Group IIIs. Removing all of the wax does not appear to be economically feasible in this price driven market, but refining mineral oils is not really my area of expertise.
Tom
The waxes were present in the starting crude oil. The relatively mild hydroprocessing used in Group II refining does not remove all of the waxes. Neither does the hydrocracking in Group IIIs. Removing all of the wax does not appear to be economically feasible in this price driven market, but refining mineral oils is not really my area of expertise.
Tom
I've done many a freezer test with various oils and I've never seen a dino with crystals precipitate out. However, Havoline synthetic looked like a snowflake there was so much crystallization!
Hi Drew,
I wouldn't expect any actual precipatation with a modern oil down to perhaps -20F, at least not in an oil intended for use at such temperatures. You may see the oil turn cloudy, but this can also be caused by other factors such a water content, organic soaps, and additives. Crystal formation and its precipitation is very dependent on the rate of cooling and just popping it into a cold bath or freezer will usually super cool the oil right past any freeze point. Even the staged cooling of the pour point test is too fast for most such crystalization.
I'm surprised that the Havoline synthetic threw a precipatate. At what temperature did this happen? I assume it's a Group III?
BTW, the PAOs and esters used in motor oils have no wax and will not crystalize at all - they have true pour points.
Tom
I wouldn't expect any actual precipatation with a modern oil down to perhaps -20F, at least not in an oil intended for use at such temperatures. You may see the oil turn cloudy, but this can also be caused by other factors such a water content, organic soaps, and additives. Crystal formation and its precipitation is very dependent on the rate of cooling and just popping it into a cold bath or freezer will usually super cool the oil right past any freeze point. Even the staged cooling of the pour point test is too fast for most such crystalization.
I'm surprised that the Havoline synthetic threw a precipatate. At what temperature did this happen? I assume it's a Group III?
BTW, the PAOs and esters used in motor oils have no wax and will not crystalize at all - they have true pour points.
Tom
My freezer is set at about 0 degrees F. It was crystaly and cloudy. Really didn't instill confidence with me, I'll say that! It was 10w-30 by the way.
Wouldn't give me a warm & fuzzy either!
Tom
Tom
So if I store my oils in the garage during the freezing months will they be o.k. come warmer temps? Or will there be some sort of permanent crystallization? In other words will my conventional oils be damaged from the freezing temps?
""BTW, the PAOs and esters used in motor oils have no wax and will not crystalize at all - they have true pour points.""
OK Tom now you are going to have to splain that one
bruce
OK Tom now you are going to have to splain that one
bruce
Hi Bruce,
Simple - neither PAO nor ester base oils have any linear waxes that crystalize. Both are highly branched and will just continue to thicken as they are cooled until they are too thick to pour under their own weight - true pour point as opposed to freeze point.
Tom
Simple - neither PAO nor ester base oils have any linear waxes that crystalize. Both are highly branched and will just continue to thicken as they are cooled until they are too thick to pour under their own weight - true pour point as opposed to freeze point.
Tom
I knew that though others would ask.
bye the way what esters do most majors use for "solvency" with GPII and GPIII/PAO or are AN's more popular?
I know what I use but wonder.
bruce
bye the way what esters do most majors use for "solvency" with GPII and GPIII/PAO or are AN's more popular?
I know what I use but wonder.
bruce
Tom NJ it is hard to add any more. You know your stuff. I have seen the same thing, but perhaps in more lay terms. Correct me if I'm wrong.
Pour point is a poor comparison specification for the real world especially of PAO synthetics and group III synthetics, and group II's. The reason is that group II and III's are parafinitic based and have the wax crystal effect as they get near the pour point.
However, with the right additives they can do very well in the CCS and MRV tests which as you graphically described is closer to real world.
So while PAO's base oils can register some amazing pour points, once you put the add pack in, and test them more realisticaly with CCS and MRV, the advantages disappear, or in some cases even reverse.
In any case as you and others have said don't look at pour point, check CCS and MRV.
But Mike, I would suggest the answer to your real question is in the 15w part. That is thick oil, and you would make the most gains in just considering a 5w, without even considering the best one based on CCS and MRV.
Pour point is a poor comparison specification for the real world especially of PAO synthetics and group III synthetics, and group II's. The reason is that group II and III's are parafinitic based and have the wax crystal effect as they get near the pour point.
However, with the right additives they can do very well in the CCS and MRV tests which as you graphically described is closer to real world.
So while PAO's base oils can register some amazing pour points, once you put the add pack in, and test them more realisticaly with CCS and MRV, the advantages disappear, or in some cases even reverse.
In any case as you and others have said don't look at pour point, check CCS and MRV.
But Mike, I would suggest the answer to your real question is in the 15w part. That is thick oil, and you would make the most gains in just considering a 5w, without even considering the best one based on CCS and MRV.
When I was living in Lewellen Nebraska, we were given warning that it was going to be very cold that night. Low in the -40 maybe -45 F. All animals should be appropriately sheltered. I believe this was back in 1989 or thereabouts.. Anyway, I put a quart each of Amsoil 10W-30, Havoline 10W-30 and either QS or Pennzoil 10W-30 (can't exactly recall now which one) out on the back steps. In the morning I got up and the temp on the thermometer read -50. F. You can't imagine how many vehicles would NOT start that morning. I removed the caps from the oil and the 2 regular oils(dino) when held upside down just stayed in the bottle. The Amsoil 10W-30 I had would pour out but was the consistency of molasses. So even though these were all rated at 10W-30 it was evident that this temp was far in extreme of what this oil grade was capable of handling. Even the 10W-30 Amsoil would have had a very difficult time flowing, but it was what I had in my vehicle, and it was able to start. Didn't want to go anywhere, but just wanted to see if it would actually start.
Many of the transformers up on the pole had tripped and had to be reset. Getting up there with hydraulic lifts was a real challenge for those guys.
It's not the only reason I've been partial to synthetics, but is is one of the strong points for me. When you come from such a climate extreme as Nebraska, you can appreciate it's broad temperature range.
It's not the only reason I've been partial to synthetics, but is is one of the strong points for me. When you come from such a climate extreme as Nebraska, you can appreciate it's broad temperature range.
The world as we know it really changes at -40 or so. This reminds me of the poster that has a tagline something like no oil is too thin at startup, and no battery is too large. I agree, but with some conditions. I have always subscribed to the large battery theory and whenever the factory install failed I would measure up the space and put in the biggest (physically and CCA) that I could find. I had a Nissan 4x4 that I put a group 27 battery in, and found myself in Saskatchewan with no place to plug in, and -43 or so weather. At the time I was using ESSO 5 or 10w40 oil. In the morning it started barely. But, two days later in not much warmer weather in Winnipeg, I was replacing the starter drive.
Conclusion? There is more to cold weather startup than just starting. No idea what other damage I did, or would do repeated starting under those conditions. But, I did sell the truck in good running order with my usual 100K plus miles on it.
My current rule with 5w30 is to plug in, if overnight temps drop below -20C (-6F).
Conclusion? There is more to cold weather startup than just starting. No idea what other damage I did, or would do repeated starting under those conditions. But, I did sell the truck in good running order with my usual 100K plus miles on it.
My current rule with 5w30 is to plug in, if overnight temps drop below -20C (-6F).
Another excellent post from Tom. I'll just throw in another measurement not usually published or discussed, Gelation Index.
LOL Ron AKA!
I used to use 5W30 in Fort St. John before I came across 0W30 from Esso in some Home Hdwre stores (roughly 3.99CAD/L). Also, recently ________ Tire also carries Q-state Winter blend (in light-blue bottle) for 0W30 or similar but asking for a premium price. I bet ya either one of those would serve us well in -36C w/o block heater!
I used to use 5W30 in Fort St. John before I came across 0W30 from Esso in some Home Hdwre stores (roughly 3.99CAD/L). Also, recently ________ Tire also carries Q-state Winter blend (in light-blue bottle) for 0W30 or similar but asking for a premium price. I bet ya either one of those would serve us well in -36C w/o block heater!
Hi Bruce,
There are lots of choices in esters depending on what one wants to achieve, but the most popular for solvency is TMP C8C10. This POE ester is relatively less expensive, has great physical properties, and high lubricity. There is a small dose of it in Mobil 1 in addition to AN. The original Castrol Syntec used a special ester designed for very high lubricity but at a higher cost, and others sometimes use adipate diesters for cost savings. Esters are very flexible and many properties can be varied according to the desired performance -- or claims.
The only oil I know of using ANs is M1 as they make it. Mobil also sells ANs on the merchant market but the prices are higher than even POEs.
Which do you use? (If you wish to disclose.)
Tom
There are lots of choices in esters depending on what one wants to achieve, but the most popular for solvency is TMP C8C10. This POE ester is relatively less expensive, has great physical properties, and high lubricity. There is a small dose of it in Mobil 1 in addition to AN. The original Castrol Syntec used a special ester designed for very high lubricity but at a higher cost, and others sometimes use adipate diesters for cost savings. Esters are very flexible and many properties can be varied according to the desired performance -- or claims.
The only oil I know of using ANs is M1 as they make it. Mobil also sells ANs on the merchant market but the prices are higher than even POEs.
Which do you use? (If you wish to disclose.)
Tom
- Status
