It seems as though the used oil concept is difficult for some. I tried to exclude exhausted, dirty oil from the discussion - without success. I will attempt to reframe the question. The reframed question is less practical, but also less prone to the "buy my dirty oil" plea.
Let's say that we had a large number of engines (of course not identical, but as close as we can get) that were connected to common machine creating common loads. Each day we drained the oil from one engine and used it to replace the oil in the next engine. The first engine would get virgin oil. (I realize that we have to assume no losses, complete drains, ect.) Our break-in period will end when the oil of he first engine is finally in the last engine. At the end of the experiment, the last engine would have run on only used oil (after break-in), and the first engine would have run on only fresh oil. All engines in between would have run on oil one day older than the last. Let's also assume that we performed the experiment enough times that we were able to get a complete experiment without a catastrophic failure that contaminated all downstream engines. We can also add that all engines draw air from a common sealed duct and that there are no vacumn leaks to get around other contamination issues. At the end of this experiment, we tear down all of the engines, measure wear, and plot a graph with wear on the X-axis and oil age on the Y-axis. Where would the lowest point on that graph be? My bet is that the continuously fresh oil engine would not be the lowest point and that the lowest wear may not be in any of the relatively early engines. My suggestion from the begining of this thread is that the lowest wear would be somewhere in the "used" oil part of the curve/line. I accept that the highest wear would be somewhere in the very used part of the curve.
I accept that above experiment is not "real world." I recognize that some will find additional assumptions that we will have to make. If you consider the above experiment, do you think that low point of the curve is at the beginning (fresh is best) or that the low point will be somewhere in the used range. I don't think anyone will predict that the lowest wear will be in the exhausted, filthy range (if they do, then TallPaul may have new business model). I am also asking you to consider the "curve" - the overall data. I recognize that the lowest point may be an anomoly and I am not really interested in anomolies.
Let's say that we had a large number of engines (of course not identical, but as close as we can get) that were connected to common machine creating common loads. Each day we drained the oil from one engine and used it to replace the oil in the next engine. The first engine would get virgin oil. (I realize that we have to assume no losses, complete drains, ect.) Our break-in period will end when the oil of he first engine is finally in the last engine. At the end of the experiment, the last engine would have run on only used oil (after break-in), and the first engine would have run on only fresh oil. All engines in between would have run on oil one day older than the last. Let's also assume that we performed the experiment enough times that we were able to get a complete experiment without a catastrophic failure that contaminated all downstream engines. We can also add that all engines draw air from a common sealed duct and that there are no vacumn leaks to get around other contamination issues. At the end of this experiment, we tear down all of the engines, measure wear, and plot a graph with wear on the X-axis and oil age on the Y-axis. Where would the lowest point on that graph be? My bet is that the continuously fresh oil engine would not be the lowest point and that the lowest wear may not be in any of the relatively early engines. My suggestion from the begining of this thread is that the lowest wear would be somewhere in the "used" oil part of the curve/line. I accept that the highest wear would be somewhere in the very used part of the curve.
I accept that above experiment is not "real world." I recognize that some will find additional assumptions that we will have to make. If you consider the above experiment, do you think that low point of the curve is at the beginning (fresh is best) or that the low point will be somewhere in the used range. I don't think anyone will predict that the lowest wear will be in the exhausted, filthy range (if they do, then TallPaul may have new business model). I am also asking you to consider the "curve" - the overall data. I recognize that the lowest point may be an anomoly and I am not really interested in anomolies.
