I did a search and didn't find anyone proposing this (maybe with good reason, lol), so I am interested in everyone's thinking. With the advent of oil extractor's using the dip stick tube it has become quite easy and clean to withdraw the oil from the pan. So, what about devising a multi-stage super-filter to run the withdrawn oil through and then putting it back in the motor? I'm not suggesting this as an alternative to proper oil change intervals, but just to have better lubrication for the second half of the interval between changes. Such a multi-stage filtering system could include a settling period for unwanted (solids) to drop down and for unburned diesel fuel to rise to the top. I'm ignorant of the chemistry as to what acid's and base's form in the oil during use, but this might be an area, too.