diesel oil - is it always dark?

[Redneck in training]

Dark oil is a sign that it is doing its job keeping the "dirt" suspended instead depositing it in some small passage and plugging it over time. I also think that the particles are small and soft and don't do damage to engine. Larger particles that are created by wear or enter the engine via vents and trough the suction are filtered out.

Bypass filter catches much smaller particles but the trade off is that it would have large pressure drop at full oil flow (it is a function of square of the oil velocity). Therefore only small portion of oil is filtered. The reason I would consider installation of the bypass filter on my tractor is just to put it on some convenient location. Removal of the filter on my tractor is a pain.

 

[valley]

Here in "OIL, FUEL and LUBRICANTS" The thread is " Bypass oil filter on car or tractor" post #11 best dicription of bypass filter and installation I have read. Take a look. I don't know how to post a link to that thread.

 

[RWEST]

I may post on the bobistheoilguy.com website and ask the pro's what they think.

The CJ-4 stuff has actually proven to work quite well for pre-'07 equipment, based on BITOG reports. Seems the revised add-pack ratios and improved base-stocks they're using are working out nicely as far as protection. Plus, the reduced ash content is a definite bonus - keeps valve/combustion chamber deposits to a minimum.

The thread is " Bypass oil filter on car or tractor" post #11 best description of bypass filter and installation I have read.
Link to post.

 

[big bubba]

Just an observation on my use of diesels re: oil color. ran MBenz diesels, Massey Ferg tractors for years, yes, the quik switch to dark after oil change. no problem. bought new Kubota L4400 & MX5000 and same thing. no worry. upgraded to a Tier 2 engine M8540 Kubota, and going on 100 hrs on a change, and the oil is honey clear like a gasser. I think the 4 valves per cyl. helps. so even within a diesel, esp w/modern designs, "soot" is a relative thing....like the idea of not seeing black between changes even though it's totally normal on conventional diesels. bb

 

[mcconoughey]

I wondered about the oil darkening situation right after we purchased our little dozer. The guy at the dealership said he had just changed the oil and it was already black as pitch.

Reading this thread I got to thinking about the soot issue and wondering if it might actually contribute some lubricating properties to the oil... After all, we put powdered graphite into locks to keep them operating smoothly. Seems to do a really good job. And all the diesel soot I've ever encountered had an almost soapy feel to it.

Is there any hard data out there that would maybe prove or disprove this theory?

Yes. Your nearest engineering college will have access to Society of Automotive Engineers (SAE) technical papers. These are grouped by years and document numbers. You will find several dozen technical papers on various aspects of oil, including the wear effects of diesel engine soot. Overly condensed, soot is bad and increases wear. The diameter of soot particles and their extent of agglomeration (sticking together) matter greatly. Good filters help. Good filters plus bypass filters help even more.

 

[sw03]

Dark oil is a sign that it is doing its job keeping the "dirt" suspended instead depositing it in some small passage and plugging it over time. I also think that the particles are small and soft and don't do damage to engine. Larger particles that are created by wear or enter the engine via vents and trough the suction are filtered out.

Bypass filter catches much smaller particles but the trade off is that it would have large pressure drop at full oil flow (it is a function of square of the oil velocity). Therefore only small portion of oil is filtered. The reason I would consider installation of the bypass filter on my tractor is just to put it on some convenient location. Removal of the filter on my tractor is a pain.

WEll I can use Rotella and it gets black..I use Amsoil and stays clean..Even in a Powerchoke with over 11,000 miles..I can use JD50 (I think) oil and get black on day 2.

Then again oil color is meaningless in terms of black vs none..

 

[sw03]

Yes. Your nearest engineering college will have access to Society of Automotive Engineers (SAE) technical papers. These are grouped by years and document numbers. You will find several dozen technical papers on various aspects of oil, including the wear effects of diesel engine soot. Overly condensed, soot is bad and increases wear. The diameter of soot particles and their extent of agglomeration (sticking together) matter greatly. Good filters help. Good filters plus bypass filters help even more.

I read the ASTM, Mil, SAE, NASM, etc daily..The do not mean much in some cases.

 

[schiker]

As several posted soot is black and stains the oil. It is bad and increases wear. Diesel rated oil has a better additive package to hold it in suspension and disperses it to reduce wear. You can't tell how much soot is it in the oil by color or looking at it or feeling it for the most part. It takes a oil analysis to determine if the oil's additive package is used up or has too much contamination.

How much is left in the engine and coolers etc will determine how quick it turns black at change. It only takes a little soot residue to stain the oil dark then black. I have a 6.5 GM diesel with external oil cooler and once the oil circulates one time on cranking it turns black. I have changed the oil almost back to back to flush all the old oil out and it took maybe 30 minutes to 1 hour to turn the oil black again.

How good the rings seal and health of injectors, IP, and air intake will determine how much soot gets in the oil over time. But generally older diesel turn black quick. Newer diesels that burn cleaner can have clearer oil longer if the previous oil is drained thoroughly but again will turn black.

Bypasses and good filters will help reduce wear but depending won't do much for color tint in a sooty engine. The soot is too small to remove all of it.

 

[fieldserviceengineer]

I wondered about the oil darkening situation right after we purchased our little dozer. The guy at the dealership said he had just changed the oil and it was already black as pitch.

Reading this thread I got to thinking about the soot issue and wondering if it might actually contribute some lubricating properties to the oil... After all, we put powdered graphite into locks to keep them operating smoothly. Seems to do a really good job. And all the diesel soot I've ever encountered had an almost soapy feel to it.

Is there any hard data out there that would maybe prove or disprove this theory?

As a field service engineer for a division of a major engine company, I can assure you that while soot and graphite are black, they are two entirely different forms of carbon. Soot is abrasive due to its structure. One of engine lube oil qualifying tests required for API specification CJ-4 and previous designations is the Cummins M11 High Soot test. That test measures the effects of wear on valve train components where the lubrication is by splash rather than as pressure fed. Soot in the oil is suspended by dispersant additives to keep the soot in solution thus it becomes part of the problem in valve component wear. When oil nears the end of its operating life, the dispersant package is less effective. This allows soot to be deposited on internal surfaces. It is this deposit combined with carry-over oil that causes the new oil to take on the black coloration of the old oil. Carry over is the residual oil that clings to internal surfaces and is trapped in the oil cooler and lube passages. On some engines like 15 liter 6 cylinder diesel engines, the carry over amounts to 1 gallon. For those who expect a bypass filter to remove soot, I must say that bypass filtration does more to remove organic combustion products than soot. Soot particles are sub micronic in size. A micron is 39 millions of an inch. There are no effective filter products that remove particles that size unless they agglomerate with oil additives to such a size as filtration can remove them. No engine full flow filter comes remotely close to being able to remove soot or even agglomerated soot. The best advice from engine companies in general is to follow their recommended oil change intervals using lubricants they recommend or lubricants that meet the engine company's engineering specifications. Even in my position as one who has been in this business for 25 years, I likely will be considered by some to be just another keyboard expert weighing in with an opinion. Never mind that the opinion is based on a large part of my work life. Go with the printed information provided by your engine and equipment manufacturer. It is their reputation that is at stake. Their desire is to build engines or machines that provide the service life and performance that will get you to want another. There are plenty of aftermarket companies (like specialty air filters offering long life and never plugging) and other products like lubricants that are claimed to be so different than the standard big name oil companies....all these companies have to sell is a marketing story. Stick with what your tractor or engine manufacturer recommends. Filters are a good example of this. Lots of claims about some filter products on the market. I have noticed a big surge in selling synthetic media filters that can remove soot. They point to black solids claiming it is soot. A small part of it is. Some centrifugal oil cleaning devices claim to remove soot. The solids accumulation they display is about 50% water combined with combustion byproduct acids, gum and varnish and a little soot.

 

[Egon]

Gee, on my Dodge Cumins the oil always looks clean on the dipstick but I do change it at regular intervals!