Oil Change questions on 300TD 2000 LWB

Black colour is normal very quickly. Remaining oil contaminates.
Sucking it out is standard proceedure for MB garages and just as good (although you could argue otherwise).
The 300 should have the service intervals on the dash. If you use the MB recommended oil there should be no reason for additional changes.

Do you like the G?

1) There is always old oil rememant in the engine, wheather, oil is sucked out, or drained out, it can never be totally drained away. So, when your new oil is added to the old it mixes with the old which turns black.

The blackness deepens in the oil over time , due to the combustion process, heat and soot generated in the oil that it has to cope with.

Engine flushing can help clean the old oil as it drains out better, but that too, will blacken, only taking longer. Other, factors can help old-oil drainage, like allowing a longer period for oil to drain out from the drain plug, but if sucking oil out, then allowing longer periods of sucking. More importantly, is to drain when the oil is hot. Naturally, safety issues are at hand and mechanics do not like getting their hand burnt, so thet may not warm the engine up throughly to drain.

2) Cost!, Our lives and our Economy, are PRICE conscious, the A-service allows only 0.5 hr, putting the vehicle on the ramp, in some cases removing engine guards takes time, hence m/benz have opted for sucking oil out. It is quicker, whilst the oil is sucked out, the mechanic can be doning other things on the list and saves time on loading the vehicle on the Lift and removing the engine guard. Sucking the oil out, removes the possibilty of potentionally having a leaky drain seal, and the time saved on checking for leaks after the work is completed from differnet levels, i.e top of engine and bottom of engine. If the garage is operating a bonus system, the mechanic is expected to the job in less time than 0.5 hours and go to the next to earn his crum, so he is not going to be sympathetic to having not drained every last drop of old oil out.

3) If you stick to the regemine of regularly changing the oil and oil filter as schedulled, every 6000 miles for early W463's diesels or 9000 or for the latter, (6 months) you are doing your job. The occassions, I would consider for any earlier oil renewal would in a combinations of poor conditions, lots of short journeys, particullay under 5 miles duration, in Winter, more so. Or taxi type use, lots of stop/start and town running conditions. Outside, of that you will be wasting your money. Mineral, as well as synthetic oils do chemically deteriorate, the optimum life is between 4000 and 4500 miles (4 months). So, the point to reiterate, oil life is not just mileage governed, but time governed, especially, when new oil is added to the old, time starts ticking away.
4) I am in favour of regularly using oil flushing with every oil change, but using in an old engine, you will need to weigh up a few things, looking at the inside of the engine from the oil filler hole, the engine should be free of heavy oily, carbon deposit built-up, dislodging this junck may block the current free oil supply to your engine or release blockage from your engine that could be determental to the oil pressure retention of oil pressure of the engine. If you have heavly carbonised oil deposited engine that aslo breaths heavily; unless you want to risk to see what happens, do not at this stage, never use engine flush. In particular, the concenrates' of small 350 cc or 500 cc tins cans available, the oil flush mixed in oil is milder, this is where you have drain half the old oil out from the engine and add the oil based flush, run engine and drain the lot, replenishing with a new.

5) Yes, but choice remains yours. I say yes, from the point of view, that the object of oil change is to have as fresh an oil in, as feesable, then, why let old oil, trapped in the oil filter contanminate your new oil?

Regards,