Re: Which Engine Oil?
Posted by Joe D'Agostino On 2018/8/21 20:14:48
One thing that has always intrigued me is the fact that all oils, regardless of mineral or synthetic and regardless of weight, fall into the same viscosity zone once they become heated. Please see the chart attached here. The viscosity is tightly grouped in the 10 to 18 range regardless of multi-weight or single weight. The same is true for synthetics.
All oils start off at widely different viscosities but end up close to each other once hot.
As we know, 90% of engine wear occurs at startup due to lack of oil on the bearings and other parts of the engine.
Straight weight oils have viscosity of around 200 at room temperature. Multi-weights are better. But most oils do not flow well at room temperature. All have somewhat limited flow characteristics.
We also know that lubrication comes from oil movement and not necessarily pressure.
So I would think that we should want as much oil movement as possible as early as possible after the dry start.
We also know that the synthetics are much better in this area than the mineral oils. A 0w-40 synthetic has a room temperature viscosity of about 60 or 70 which is much lower than any multi weight mineral oil.
I know that some of the experts will say that we should never put a 0 weight oil in our cars but if the viscosity of the 0 weight is 60 or 70 at room temperature, that is still 6 or 7 times the viscosity of the oil when it is hot.
Since all oils tend to flatten out in the same viscosity region at operating temperature, it would make sense that we all use the lightest weight multi-weight oil to get the best lubrication at startup.
After warm up, we will be getting the same lubrication at operating temperature from all oils as we can see from their viscosity plots.
In other words, why wait for the oil to thin out at 70 or 80 degrees C to get the best oil flow? Why not start with better oil flow at a lower temperature? After all, they are all ending up at roughly the same viscosity.
I just had my engine rebuilt and the rebuilder told me to use straight 30 weight mineral oil for diesel engines with zddp. While I liked the suggestion of the zddp, the flow of this oil is around 200 at 75 degrees F. I followed his recommendation for the first 1000 miles but then I switched to classic car motor oil 15w-40 since it is thinner at room temperature (it is a mineral oil and also has the zddp).
I realize that the cam lobes in our Packards are rather low in height and we may not really need the zddp but I like it for added protection.
I realize that some old engines with lots of miles on them need some thickness in the oil for protection. Couldn't this be achieved with a multi-weight synthetic that can be purchased with a thicker upper value?
I post this as food for thought.
Attach file:
(36.18 KB)
All oils start off at widely different viscosities but end up close to each other once hot.
As we know, 90% of engine wear occurs at startup due to lack of oil on the bearings and other parts of the engine.
Straight weight oils have viscosity of around 200 at room temperature. Multi-weights are better. But most oils do not flow well at room temperature. All have somewhat limited flow characteristics.
We also know that lubrication comes from oil movement and not necessarily pressure.
So I would think that we should want as much oil movement as possible as early as possible after the dry start.
We also know that the synthetics are much better in this area than the mineral oils. A 0w-40 synthetic has a room temperature viscosity of about 60 or 70 which is much lower than any multi weight mineral oil.
I know that some of the experts will say that we should never put a 0 weight oil in our cars but if the viscosity of the 0 weight is 60 or 70 at room temperature, that is still 6 or 7 times the viscosity of the oil when it is hot.
Since all oils tend to flatten out in the same viscosity region at operating temperature, it would make sense that we all use the lightest weight multi-weight oil to get the best lubrication at startup.
After warm up, we will be getting the same lubrication at operating temperature from all oils as we can see from their viscosity plots.
In other words, why wait for the oil to thin out at 70 or 80 degrees C to get the best oil flow? Why not start with better oil flow at a lower temperature? After all, they are all ending up at roughly the same viscosity.
I just had my engine rebuilt and the rebuilder told me to use straight 30 weight mineral oil for diesel engines with zddp. While I liked the suggestion of the zddp, the flow of this oil is around 200 at 75 degrees F. I followed his recommendation for the first 1000 miles but then I switched to classic car motor oil 15w-40 since it is thinner at room temperature (it is a mineral oil and also has the zddp).
I realize that the cam lobes in our Packards are rather low in height and we may not really need the zddp but I like it for added protection.
I realize that some old engines with lots of miles on them need some thickness in the oil for protection. Couldn't this be achieved with a multi-weight synthetic that can be purchased with a thicker upper value?
I post this as food for thought.
Attach file:
(36.18 KB)
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