diesel oil - is it always dark?

[eastexan]

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.
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Perhaps.....but in my old 1973 Ford 3000 that I bought 2 years ago, the oil
was clear when I bought it, and had turned a dark honey color by the time I changed it 2 weeks ago. But it had never turned black.
Since the oil change, it has stayed clear, even after using it hard while brush hogging tall Bahia pasture grass and sprouts.

Black diesel oil doesn't concern me. That's normal with diesels. I'm retired now, but have been around diesels most of my life on my job. But I've never seen one with clear oil until now. From what I've seen, clear oil is not the norm with diesels. If the oil had been black, I wouldn't have given it a second thought.
I'm a little concerned about it, but mostly just curious as to why the oil stays clear. I might have thought that perhaps low compression could be causing it, but it seems to have plenty of power. The only thing that halfway makes sense to me is if the guy that had it before me had always changed the oil way earlier than he needed to, and therefore it stayed clean. But that don't make sense either, because I've seen new vehicles that got black oil pretty quick after being used.

 

[sw03]

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.

Oh boy...Great for you...

When someone posts I have worked blah blah, I lose faith..show facts.

 

[sw03]

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.
------------------------------------------------------------------------

Perhaps.....but in my old 1973 Ford 3000 that I bought 2 years ago, the oil
was clear when I bought it, and had turned a dark honey color by the time I changed it 2 weeks ago. But it had never turned black.
Since the oil change, it has stayed clear, even after using it hard while brush hogging tall Bahia pasture grass and sprouts.

Black diesel oil doesn't concern me. That's normal with diesels. I'm retired now, but have been around diesels most of my life on my job. But I've never seen one with clear oil until now. From what I've seen, clear oil is not the norm with diesels. If the oil had been black, I wouldn't have given it a second thought.
I'm a little concerned about it, but mostly just curious as to why the oil stays clear. I might have thought that perhaps low compression could be causing it, but it seems to have plenty of power. The only thing that halfway makes sense to me is if the guy that had it before me had always changed the oil way earlier than he needed to, and therefore it stayed clean. But that don't make sense either, because I've seen new vehicles that got black oil pretty quick after being used.

Use a better oil dude..I also live in TX (katy) and see it all the time.

 

[WH401]

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.

With some engines this may be true, though I have never experienced it this way. I have see it happen in the opposite way, particularly with the 5.9 Cummins. With my 92', when you put new oil in the crankcase it will stay a golden honey color for about the first 1500 miles. After that it starts to turn a slight shade darker, but still stay's light enough so that you can see through the oil to read the dipstick. When you drain the oil it has become a complete black color though.

On my 06, when you fill the crankcase with new oil, it turns blacker than road tar immediately after the first time you start it. While it may be a cleaner burning engine, one of the added components to obtain this cleaner burning is the initiation of a 3rd injection event per stroke. This extra injection creates very, very fine soot particles, that immediately just turn the oil so black that you can hardly read the dipstick. There is not a problem with this though, in fact the oil change interval on that model engine is 15k, where as the 92' is 5k.