Just curious

[Exsailor]

At the risk of showing my ignorance... Why is the motor oil
in Diesels always black? After a couple hundred miles
after an oil change it is black as tar. My cummins was the
same way.

[Javi]

Short answer is SOOT that gets by the piston rings during compression...

[Ken / Claudia]

Both of my fords have been the same a 96 and the 01. I asked someone at some point and remember that person saying it had to with the turbos. If that is true or not I do not know. Answer #2 seems reasonable.

[davidjsimons]

Short answer is SOOT that gets by the piston rings during compression...

Higher fuel injection pressures produce lower emissions but as a result produce more soot. The oil is capturing the soot and it is then filtered by the engine oil filter. This is normal. Older engines with lower injection pressure did not produce as much soot. This is why routine and timely servicing is important on these newer engines.


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[jsmith948]

X2 on the soot. Diesel is the name of the German inventor who perfected the compression ignition engine. By definition these engines have a very high compresion ratio (16:1). During combustion, some of the soot gets by the rings and into the crankcase. The 400 Big Cam Cummins I drove in the 70's, and every diesel engine I've driven since, has had black oil. Change when due and enjoy!:)

[rjsurfer]

The oil on my 2003 Cummins HO is NEVER black even after a 10,000 mile oil change. And I'm running a Bully Dog programmer set for Tow Mode.

I think my Kia has dirtier oil after 5,000 miles.

Just sayin.....

Ron W.

[davidjsimons]

The oil on my 2003 Cummins HO is NEVER black even after a 10,000 mile oil change. And I'm running a Bully Dog programmer set for Tow Mode.

I think my Kia has dirtier oil after 5,000 miles.

Just sayin.....

Ron W.

I have to second this. I may get a dark brown but never really black.


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[2011 keystone]

my oil is jet black within the first week after changing it.

[Jim W]

The newer diesels have what is called exhaust gas recirculation (EGR) on them to help meet emission rules. This means a portion of the exhaust is routed back (cooled) to the air intake system; these gases will enter the engine oil under compression. There is also a 5 or 6th fuel injection depending on engine make that is used to burn off the soot in the DPF this too will allow un-burnt fuel too enter the engine oil when the exhaust valves are open. That is why it is so important to change the engine oil as recommend by the engine manufactures.

Jim W.

[Javi]

I drove Dodge Rams from 1989 until 1998 and everyone of them turned the oil black within a 100 miles after a change... Ran Delo and changed oil every 5K religiously... which was about every two to three weeks....

I quit Ram when they dropped the B motor.. the 24 valve sucked...


My Ford 6.7 also blackens the oil quickly...

[Charli]

I checked my oil a few weeks after the last change and was curious why the oil was black. Now I know it's not a problem.
On a related matter how often do you change the oil. My manual says every 7500mi/12000km, with a minimum of every 6 months regardless of mileage, yet the dealer suggests every 6000km. I don't put on a lot of miles (about 10-12000km /yr) especially in the winter, but all of my driving is highway with a 5er in tow during the summer. My oil change indicator light has never come on (I went as high as 9000km once) and at $120. per oil change I don't want to waste my money, although its cheaper than a new engine.
I would think that the oil change indicator light is there for a reason and if it isn't on and I haven't exceeded the 12000km or 6 months I should be ok.
Thoughts?

[Javi]

I checked my oil a few weeks after the last change and was curious why the oil was black. Now I know it's not a problem.
On a related matter how often do you change the oil. My manual says every 7500mi/12000km, with a minimum of every 6 months regardless of mileage, yet the dealer suggests every 6000km. I don't put on a lot of miles (about 10-12000km /yr) especially in the winter, but all of my driving is highway with a 5er in tow during the summer. My oil change indicator light has never come on (I went as high as 9000km once) and at $120. per oil change I don't want to waste my money, although its cheaper than a new engine.
I would think that the oil change indicator light is there for a reason and if it isn't on and I haven't exceeded the 12000km or 6 months I should be ok.
Thoughts?
For me it depends on how/where I'm driving... If I'm doing a lot of towing in the Texas heat then 5K, winter months 7.5K... I drive daily and Texas winters aren't cold very often. I drive far enough to get the motor to full temperature before reaching my destination and don't idle very long so condensation isn't a big problem...

[GMcKenzie]

My 94 GMC with the 6.5L would turn black at the oil change place. 2 minutes of running was enough to turn it black.

My 01 GMC with the Duramax can go 6 months between changes and rarely looks black.

Others have theirs go black within a few hundred miles.

Doesn't seem to me to be any rhyme or reason,.

[Jim W]

I checked my oil a few weeks after the last change and was curious why the oil was black. Now I know it's not a problem.
On a related matter how often do you change the oil. My manual says every 7500mi/12000km, with a minimum of every 6 months regardless of mileage, yet the dealer suggests every 6000km. I don't put on a lot of miles (about 10-12000km /yr) especially in the winter, but all of my driving is highway with a 5er in tow during the summer. My oil change indicator light has never come on (I went as high as 9000km once) and at $120. per oil change I don't want to waste my money, although its cheaper than a new engine.
I would think that the oil change indicator light is there for a reason and if it isn't on and I haven't exceeded the 12000km or 6 months I should be ok.
Thoughts?

Are you stock?
If you are the EVIC will tell you when to change the oil; this is an algorithm program that takes into account the number of stop/starts and if you do a lot of city driving. The oil may need to be changed as often as 3000 miles (4800km) or 4500 miles (7250km) depending on if you use the truck as a grocery getter. If you do straight highway driving and towing as the 6.7L engine was designed to do this should be changed every 7500 miles. Fuel filter should be changed every 15,000 Miles.

I use to have to change my oil about every 3000 miles when I was stock in the winter months not towing and around 4500 miles in the summer camping and towing. Now I change every 7500 miles regardless of the season since the engine was reworked and improved back in late 09.

I would also change your oil yourself using a Fleetgaurd Stratapore oil filter part number LF16035 $13.50 each from Geno’s Garage and three gallons of either Shell Rotella-T 15W-40 at $13.79 each or Mobile Devaco 1300 15W-40 for $11.00 each. This way you get to know the truck and see if anything is leaking or weeping on the engine.

Jim W.