rockcrawler304

I am fairly new to diesels. I have been around them and done some work on them in the past but this is my first brand new one to own.

It just turned 3000 miles and checked the oil again and it is already real black. Is it normal for a new engine to turn the oil black so quickly? I will be doing the first change this weekend but just wanted to make sure this is normal.

Thanks
rockcrawler304

HdPower

Yes....completely normal. It will get black pretty soon after you change it.

telephonman

When I change the oil in mine, I start it check for leaks,shut it down and check fluid level its all ready black.

RowJ

Much higher compression in the cylinders causes more exhaust gas to blow by the rings. Hard to keep it looking new!

Color does not indicate wear on diesel oil...like it does in many other motors!

RJ

rockcrawler304

Thanks for the responses. I do feel better now.

AkitaSumo

I thought it was to make it easy to take that first reading on the ole dipstick!

Buffalo

I've been changing the oil in my '03 at 8000 mile intervals, using Chev. Delo-400, 15X40 (conventional oil).

The last two changes, I, also, had an oil analysis done on a sample. Both analysis's came back with the oil still being in good shape. (The '03 does not discolor the oil as rapidly as some of the newer engines).

For your comfort level, you may consider oil analysis to take away the fear that the oil is getting too dirty. Analysis may give you the confidence to extend your oil drain intervals, also. It may save you some dollars by not doing oil changes, prematurely.

The new oils are very good, today. However, be sure that you use the correct oil for your truck engine. I believe that the "CI-4+" rated oil is the one that you want to use. It has additives, in it, that suspend the soot particles so that the filter can do its job more effectively. The soot particles bind together (agglomerate) & once they are large enough, the filter should remove them. Soot particles, themselves, are very small & are not supposed to do any damage. Just look bad.

Joe F.(Buffalo)

no_6_oh_no

Good guess but if that were true we would have a lot bigger problems. The compression is not enough higher to cause that kind of sooting.

There is one thing the later CR's have that the early ones don't....third injection event. Between the EGR effect of the 3rd event and 325 hp rating the oil just gets dirty faster. I have a 92 that used to be very clean until 5k to 6k miles. Now that it is running at orslightly above my 05's power levels the oil will turn black in less than a 1000 miles.

The content of the newer oils is such they will hold lot more soot before breaking down. Just the consequences of the EPA demanding compliance.

Buffalo

My understanding of the "Third Injection Event" is that it is designed to "fire" as the exhaust valve opens, allowing the heat generated to heat up the Catalytic Converter. Apparently, they work better when very hot.

Loe F.(Buffalo)

rockcrawler304

Thanks for the information and advice.

RowJ

Sorry, but I don't follow some of your points.
A- The combination of higher compression and compression ignition causes 1-more blow by... and 2-more unburned fuel (contaminants) to get into the oil. This has always been true.
B- Yes a third injection event will get oil dirty faster... but where is the 'dirt' coming from, if not blow-by? How else can new oil get black in a clean, fairly new engine?
C-Soot in the oil is NOT what breaks it down. Soot, within reasonable levels will be held in suspension by the dispersant additives and either caught by the filter or drained out at the next oil change.
Oil 'breakes down' when additives are depleted to the point where they can not clean, cool, seal & lubricate the engine (4 functions of an engine oil).

IMHO, what attacks the oil is acid.... not soot! Primarily Sulfuric acid. Where does the sulfuric acid (H2SO4) come from.... sulfur in the diesel fuel combines with water in the hot combustion process (breaking it down to gases - H2 and O4). All this happens above the rings and enters the engine oil by drip down after being turned off or being pushed by the rings, ie blowby.

And to answer the next question from those reading carfully... the water in the combustion cycle comes from condesation - heating and cooling of the intake air during combustion.
Catapillar did a 20 yr study in the 1950's and one of their findings was very interesting! They showed that a diesel engine produces one gallon of water for every gallon of diesel fuel consumed.

The other VERY interesting finding from this study was that 90% of engine wear is caused by acid action, and not friction! I suspect that improvements in engine oil additives have changed this percentage since then.... if operators change their oil before it's PH turns acidic!

Sorry, this got a lot longer than planned!

RJ

Peterbilt

RJ,

Enjoyed reading your interesting post. So, do you think the ULSD will have a less acidic affect on the oil. I hope you don't mind a little humor (probably very little), but couldn't Cat only do a 10 year study in the 50's :>).

Pete

RowJ

Good catch!

I actually saw that and thought of correcting it but figured nobody was going to read that far anyway.

Let's try "20 yr study...starting it the 50's

RJ

timcasbolt

Diesel engines have gas-ported pistons, which is why the rings last so much longer than gas engines. It's also why they have very little blowby. Much less than gas engines, even when the diesel engine has many more miles of use.

no_6_oh_no

A - That would be true if the differences were greater AND the ring sealing was not taken into account. The difference from 14 to 17 to 1 is neglible when you consider the changes in the combustion cycle. You have to remember the CR engine runs multiple events for a couple reasons, to limit cylinder pressures and the creation of pollutants. I would hazard a guess a hopped up 12V with a bunch of timing is seeing much higher cylinder pressures than a stock CR and it's cylinder pressures that are going to cause blow-by not the compression rato. Also, if there was more unburned fuel left over that was causing the sooting they would never meet emissions.

B - Ah yes, the 3rd injection event. The common theory floating around is it is to keep the CAT hot. Well, I am sure the effect of the event does that quite well, but, that is not what it is for. Ever wonder how Cummins managed to design an engine that has more power, a wider TQ band, and still meet emissions? Without EGR? When every other manufacturer has to use EGR? What does EGR do to oil? It soots it faster. Go dig up the Cummins description of the 600/610 CR engines, then dig up the specs on the 3rd injection event and the valve timing and compare it to the early CR and 12V engines. That 3rd event is a double edged sword. Part power, part emissions, and part EGR. EGR = soot in the oil.

C - Once the oil cannot hold any more soot it breaks down. If its not holding the soot then it is not doing its job no matter how good the rest of the additives are, wgich are probably toast anyway from combining with the extra soot to create all kinds of nasty compounds. Take a look at the differences between CI and CH oils and ask yourself why Cummins reccomends the later oils that hold more soot.


As far as the sulphur combining with water to form acid, how is that happening in an environment where water is not a liquid? Yeah, yeah, water can exist in higher temps under higher pressures but the amounts left over after scavenging the cylinders with 10 to 30 psi of boost plus the extremely low content of sulphur in even LSD fuel makes a rather small impact. Another reason not to idle too long with low combustion temps.


What you proposed makes perfect sense. In the 50's, 60's, and probably 70's but fuel formulation engine technology have cleaned up a lot of the problems we used to see with diesels and gas engines. Its just not the same thing anymore.