Dirty oill and crapped out oil are two different things. His oil is completely clean with the consistency of water. I've seen this before. Wouldn't hurt to cut the filter and take a looksy..
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Thermal Degradation
When motor oil is heated beyond a certain temperature, it will start to degrade, even if there is no oxygen present. This is called thermal degradation and causes the oil to change viscosity (a form of oil breakdown). The thermal stability of motor oil cannot be improved by use of additives.
Shearing
Many people use the term “oil breakdown†to represent what they think is a motor oil that has “broken down†and is in need of changing, when in reality the actual process of “ oil breakdown†is not properly understood. The correct word for this is oil breakdown due to shear forces. An internal combustion engine imparts high shear forces on motor oil, which is sandwiched between two rotating or sliding forces under load and heat.
The molecular structure is essentially torn apart by these mechanical shear forces. The component of the oil that is affected most by these shear forces is the viscosity improvers. These viscosity improvers allow the manufacturer of the oil to create multi-grade oils suitable for a wider temperature range of operation. The end result of these shear forces is a decrease in the viscosity of the oil, as well as a decrease in the viscosity index.
Once motor oil has sheared beyond a specific point it will not revert back to it’s base structure when it cools down and the shear forces have ceased. This applies to petroleum oils only, synthetic motor oils are extremely resistant to the detrimental effects of shear forces. Another way to explain this phenomenon is as follows: If you look at the molecular structure of motor oil under a microscope, you will see chains of molecules grouped together and linked together. The smaller molecular particles are attached to the larger ones. As oil shears, these smaller molecules break away and align in the chain.
As engine heat and shear forces continue and increase, these molecules break away from the base structure and, in the process, provide less and less resistance to wear. If this shearing and excessive continues over an extended period of time, engine damage can occur. If shearing is only mild, then when the oil cools down the structure will revert back to its original structure and still be capable of providing proper engine protection. Multi-viscosity petroleum motor oils are more susceptible to shearing than straight weight petroleum motor oils. As previously mentioned, synthetic oils are extremely shear resistant and less prone to oil breakdown.
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I firmly believe this is what is happen to your motor due to the tight bearing clearance causing the shearing to begin with being compounded by thermal degradation not allowing the oil to reconstruct completely upon cooling. The end result of this is CLEAN OIL WITH THE CONSISTENCY OF WATER. Heavy weight oil is not a solution. Today's motors are built with very tight clearances, hence the need for 5w30 oils with lots of additives. I would not run anything heavier than 10w40 and make it synthetic if possible. Another cause, actually the most common cause of shearing is tight cylinder to wall clearance. I didn't measure that and assumed Calvert had it right.
Call Wayne Calvert and ask him what oil you should be running. He picked and machined all the parts in that motor. I just assembled it. I'll bet money oil pressure comes back with a new jug of Rotella in it. Both of my motors were the same. Great oil pressure with new oil every time out that faded quickly. You got 20psi back when you changed the filter, but guaranteed, it was because the oil cooled off and partially reconstructed. The filter had no dog in the fight on that one. If the old one was plugged it will bypass anyway.
