240 Ed:
Yep, I remember re-cycled oil very well just as you described - in the one quart glass jars with the funnel screwed on just waiting for someone to buy it for 5-10 cents a quart as I recall, no brand name or any reference to its origin. We could even buy it in bulk by the gallon or 55-gallon drum for less. Seems to have worked OK, but I vividly remember pulling the valve cover off several engines to find what looked like a layer of grease in the shape of the valve cover and areas without the crud only because the rockers arms and valve springs moved - the mess was even worse in the oil pan.
To those that show great concern about getting every drop of old oil out of their diesel engines during an oil change - you are overlooking the injection pump which holds about 16 ounces of oil that does not drain out (the oil outlet is either a small slit or two holes- depending on the IP version you have - located about one inch above the IP cam shaft). Partially removing the fuel pump will allow draining of the oil in the IP, then you need to refill it through the IP oil inlet, of course you may also need to replace the fuel pump gasket before putting oil in. Then you need to drain all the oil out of the oil passages and oil pump - so you need to run the engine for 30 seconds or so without any oil in it to get the very last drop of old oil out (I know someone who does this). Of course, running the engine without any oil in it to drain the passages and oil pump is COMPLETELY at your own risk - as I hope all that read this paragraph realize that this is very much tongue in cheek!
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I have not read any info from M-B about draining oil lines, the oil cooler, IP, etc., etc. Only that you should lift the oil filter up to release the oil in the filter/cannister and then remove the drain plug, then replace/renew those items needing it, refill with the appropriate weight/brand/service classification/amount of oil, run the engine to circulate the new oil thoroughly, and then check the level to make sure you have the correct amount in the engine. M-B lists no other steps for an oil change and they should know what they want done for an oil change to ensure our diesel engines will last 500,000 miles or so.
Larry Bible has it right, change the oil and filter often, and when the oil is hot. For those of you that do not know - oil takes anywhere from 15 to 30 minutes to reach operating temperature (longer in cold weather) and I prefer to run it longer at operating temperature to let the oil additives do their work (like 10-20 minutes or longer) before I drain it. Oil temperature lags behind coolant temperature when the engine is first started for the day, meaning the oil temp. will take longer to reach operating temp. than the radiator's coolant.
My, very cheap, $0.02 worth!
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Tom