Very dark oil immediately after change ('74 240D)

[FieroGT42]

Still messing with my dad's '74 240D project, destined to run on biodiesel from waste vegetable oil. Currently still on pump dino-diesel.

The oil was very black when we got the car, so I changed it and my dad has driven it some since then. I checked it again last week, and it was black again. Just working some of the old crud out from the previous owner, right?

I changed the oil again, backed the car off the ramps and had lunch. When I checked the oil level, it was very dark already! I suspect the engine has quite a bit of blowby, but it shouldn't be this dark after just letting the engine run for 2 minutes, should it?

Any guesses as to what's causing this? Is it picking up sludge from the oil pan or front mounted oil cooler? I know engine flushes can pretty much kill an engine, but is there some safe type of flush or cleaning agent I can run? Thanks.

Jason

[bgoin]

Originally Posted by FieroGT42

Still messing with my dad's '74 240D project, destined to run on biodiesel from waste vegetable oil. Currently still on pump dino-diesel.

The oil was very black when we got the car, so I changed it and my dad has driven it some since then. I checked it again last week, and it was black again. Just working some of the old crud out from the previous owner, right?

I changed the oil again, backed the car off the ramps and had lunch. When I checked the oil level, it was very dark already! I suspect the engine has quite a bit of blowby, but it shouldn't be this dark after just letting the engine run for 2 minutes, should it?

Any guesses as to what's causing this? Is it picking up sludge from the oil pan or front mounted oil cooler? I know engine flushes can pretty much kill an engine, but is there some safe type of flush or cleaning agent I can run? Thanks.

Jason

You can drop the oil pan and see or next time you drain the oil get a small wire and make a loop and put it in the drain hole (trying to bend it down on the oil pan bottom) and then pull out and see if you get a lot of sludge/crud on it.

[cmitch]

Engine flushes are pretty much a damned if you do or don't scenario. Lots of cases like yours that the engine really needs it but, what do you do?

I got the same thing with my 99 ML430. Change the oil and one trip in it and the oil was tar black. I thought after 2 years of 3000 mile oil changes, I'd worked it all out but it didn't. My vehicle consumed 1 1/2 to 2 quarts of oil per month and rattled every morning on cold crank-up for about 5 to 10 minutes! I had enough. I got some GUNK motor flush and warmed the engine for about 4 minutes and then shut it off, poured the stuff in and then cranked her back up. I let it run about 10 minutes afterward. I drained the crud out (and it was alot!) and refilled with Mobil 1 10W40. It hasn't used a drop of oil since, no rattles and the oil stays clean.

Now, don't think this will be everyone's result because I've seen engine flushes go bad as well. A Pontiac Parisienne filled the valve covers full on a friends car. There was so much crud it stopped up the drain back ports. It was a god awful mess, too. He had me help him remove the valve covers and oil gushed out down the side of the engine. It took a coat hanger and nearly a case of WD40 to clear out the drains on one of the heads. I found out that he poured the motor flush in a COLD ENGINE and then cranked it up. I don't know for sure if the results would have been different had he warmed it up first, but I think it would.

If you do decide to flush, be aware it could do this. Be prepared to take off valve cover and deal with a huge mess if it doesn't work out. If it were mine, I'd do the flush but only on a warm engine but that's me. There are just as many here who would be adamant about NOT flushing it.

[CalifSLK]

Originally Posted by FieroGT42

...

The oil was very black when we got the car, so I changed it and my dad has driven it some since then. I checked it again last week, and it was black again. Just working some of the old crud out from the previous owner, right?

I changed the oil again, backed the car off the ramps and had lunch. When I checked the oil level, it was very dark already! I suspect the engine has quite a bit of blowby, but it shouldn't be this dark after just letting the engine run for 2 minutes, should it?

Any guesses as to what's causing this? Is it picking up sludge from the oil pan or front mounted oil cooler? I know engine flushes can pretty much kill an engine, but is there some safe type of flush or cleaning agent I can run? Thanks.

Jason

Black oil is normal for a diesel. This was when I stop changing oil after getting it all over myself the first time.

[POS]

Very normal.

[Nimrodthewombat]

Ditto. When I got my first diesel I got hysterical because the oil was always black! A good friend of mine who was an MB tech for 35 years said it's because you can never really FULLY drain all of the oil out. About a half a quart remains in the oil cooler and lines and when you start the car up after the change it mixes with the new causing the black


Don't worry about it.

[Yacht Master]

Originally Posted by FieroGT42

Still messing with my dad's '74 240D project, destined to run on biodiesel from waste vegetable oil. Currently still on pump dino-diesel.

The oil was very black when we got the car, so I changed it and my dad has driven it some since then. I checked it again last week, and it was black again. Just working some of the old crud out from the previous owner, right?

I changed the oil again, backed the car off the ramps and had lunch. When I checked the oil level, it was very dark already! I suspect the engine has quite a bit of blowby, but it shouldn't be this dark after just letting the engine run for 2 minutes, should it?

Any guesses as to what's causing this? Is it picking up sludge from the oil pan or front mounted oil cooler? I know engine flushes can pretty much kill an engine, but is there some safe type of flush or cleaning agent I can run? Thanks.

Jason

That is just the way it is, no problem, normal. Not a good idea to flush a diesel.

[FieroGT42]

Ok then, thanks. I won't let my dad get the engine flushed, but I think I'll drop the oil pan next change and clean any sludge, maybe blast something through the oil cooler to make sure the passages are clear.

[mrhills0146]

Originally Posted by FieroGT42

Ok then, thanks. I won't let my dad get the engine flushed, but I think I'll drop the oil pan next change and clean any sludge, maybe blast something through the oil cooler to make sure the passages are clear.

Overkill. Not necessary - the only reason you'd have a sludging problem is if previous owner either never changed the oil or rarely changed it w/ non-Diesel rated oil.

If you insist on going overboard, you can run a full synthetic oil which has some solvent/detergent-like properties. But even that is really unnecessary on an old robust car like you're dealing with.

[mdvijay]

Originally Posted by CalifSLK

Black oil is normal for a diesel. This was when I stop changing oil after getting it all over myself the first time.

agree as above...diesel oil will turn black

vijay