Engine/Transmission (1994 - 1998) Noob question: Why fresh oil stays so clean?

[Roamer]

I just purchased my 2001 with ~101k miles and did my first oil change with a Fleetguard filter. I have ~500 miles on that oil now and I'm stunned that the oil is still clean and transparent. I've owned two other diesel vehicles (a Mercedes wagon and a VW wagon) and in both cases the new oil would immediately turn completely black with soot after the very first startup. Why hasn't this happened with my Dodge? Is there something different about the filtration or blowby on my truck that keeps the oil so clean?

EDIT: Ooops, sorry, just realized I posted in the wrong forum. This should go in the 24-valve forum. Mods, please fix if you can.

 

[SnoKing]

I think it has to do with CJ-4 oil not collecting stuff and moving it around to the filter and being dumped at oil changes. At 100-200K we may find sludge in our engines like the days before high detergent oils. I first noticed this in my two B150's in the boat a few years ago, in that the oil did not get dirty. They had 2000 hours on them the first time I did not chase down CI-4+ oil. And it is getting harder and harder to find.

SNOKING

 

[JR]

Actually CJ4 oils are more capable of holding soot in suspension than the older CI4 oils. The belief is that the higher TBN of the CI4 oils make it a better oil than the CJ4 but the high TBN was needed to help neutralize the 500PPM sulfur content in the fuel At the time. Since the inception of ULSD high TBN content is not nearly as critical as it used to be.

As for your question as to why the oil stays cleaner, there is no EGR on the Cummins engine compared to your VW and Mercedes. As long as your injectors are within spec and you have good compression you can expect your oil to stay fairly clean for many miles to come. At 7500 miles my oil is still a dark honey color, and I have been using CJ4 oil for several years.

 

[mfurrh55]

My 07 5.9 turns black pretty quick after oil change and always has, so did my 01 dually, i even run an oil bypass system on it , still turns black fast

 

[SierraRam]

My 03 & 07 turned black very quickly.

 

[JR]

The 04.5 and up CR engines are very different from the OP's engine in question.

 

[AH64ID]

As JR said the CJ oil holds more soot than previous oils, which makes it hard to filter out.

The main reason is the design of the motor vs emissions, it allows the oil to stay clean.

 

[KBurgoyne]

Mine doesn't start to turn black until 3500-4000 miles. It also has zero emissions garbage to run exhaust back through the system. You might have a capped EGR. Its a good thing.

 

[JR]

The OP does not have EGR on his engine.

 

[fest3er]

... As long as your injectors are within spec and you have good compression you can expect your oil to stay fairly clean for many miles to come. ...

I'll bet the most common cause of soot in the oil is blow-by. Conversely, 'clean' oil indicates almost no blow-by. I would expect over-fueling and poor atomization to create higher quantities of soot; that in turn increases the probability that soot will get by and into the oil.

 

[SierraRam]

Wow I guess I had blow by on both of my truck when new...

 

[mfurrh55]

Wow I guess I had blow by on both of my truck when new...

Same here, some don't know what they are talking about

 

[fest3er]

Wow I guess I had blow by on both of my truck when new...

Yes, you did. That's why the crankcase breather tube is there.

 

[SierraRam]

Yes, you did. That's why the crankcase breather tube is there.

Yep along with everyone else.

 

[Roamer]

Thanks for the replies, very interesting. JR's explanation seems the most likely to me; I didn't know my truck doesn't have an EGR (shows you how much of a noob I am with these trucks).

As for your question as to why the oil stays cleaner, there is no EGR on the Cummins engine compared to your VW and Mercedes. As long as your injectors are within spec and you have good compression you can expect your oil to stay fairly clean for many miles to come. At 7500 miles my oil is still a dark honey color, and I have been using CJ4 oil for several years.