Castrol ran a test that shows that oil degrades much faster when running it a quart low in the crankcase. I do not have any other information from the test other than the blurb below. Draw whatever conclusions from it that you want to. It is after midnight and I am at work and bored.
Les
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Top-Up Demonstration
We have run a program to compare the rate of oil degradation when the car is run at near
maximum versus near minimum dipstick oil level. It has shown conclusively that when run at the near minimum mark, the oil degrades at a significantly higher rate compared to the near maximum level. The measured degradation was most significant in respect of wear protection, HTHS viscosity (fuel economy impact) and low temperature, CCS, viscosity (start up).
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Les
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Top-Up Demonstration
We have run a program to compare the rate of oil degradation when the car is run at near
maximum versus near minimum dipstick oil level. It has shown conclusively that when run at the near minimum mark, the oil degrades at a significantly higher rate compared to the near maximum level. The measured degradation was most significant in respect of wear protection, HTHS viscosity (fuel economy impact) and low temperature, CCS, viscosity (start up).
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