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 So, what about devising a multi-stage super-filter to run the withdrawn oil through and then putting it back in the motor?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.

Imagine, if you will, how incredibly cheap your system would have to be to make economic sense in lieu of regular oil changes.

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1989 300 SEL that mostly works, but needs TLC

I think regular frequent oil changes are good enough. If you change the oil often enough, you won't need to remove all the impurities from the oil, and during the life of the oil the oil filter should handle anything that needs to be removed.

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Ali Al-Chalabi

2001 CLK55
1999 Dodge Ram 2500 Cummins Diesel
2002 Harley-Davidson Fatboy
Merlin Extralight w/ Campy Record

Point well taken that it is impractical and costly in time and money compared to just changing oil at regular intervals. I didn't intend to imply that such an offboard filtering system be used to lengthen oil change intervals though. I do thank you for your replie's.

aftermarket bypass oil filter systems are around.

check out some Amsoil sites for automobile aftermarket designs. Not something I would use.

I think cummins, international etc. use bypass or dual filter systems.