Why does Oil color change?

[Wacky]

Ok, I probably should know this....but...I have 12 hrs on my new machine and was noticing a change in the color of the oil:
1 Why does oil change colors from golden to black in diesel engines much quicker than gas engines??
2 Is the oil under higher heat or more stress, than the gasoline engines??
3 Should one change oil more often when is is "black" ?
I would think the protective properties of the oil, when it is black, are gone.
And, I cannot believe this engine only takes about 3 quarts of oil?! How does it stay cool enough.

 

[amigauser]

Diesel engines put a lot of soot into the oil. That is what turns it black. The soot is held in suspension in the oil until it is changed. The diesel engine specific oil has properties to assist with this. That is one of the many reasons not to use an oil that is not diesel rated in a diesel engine. Just because it is black in color does not mean it has gone bad. Change the oil based on your manufacturer recommendation.

 

[Wacky]

Things have changed over the years. The tolerances must be a lot tighter because I now am told to use 10w30 in this tractor, whereas 15w40 on an old Ford 3000. I just wonder winter use vs. summer use I would think the 10w30 would break down much easier than the 15w40? I just am looking at the longevity of my equipment, I want to think thicker is better in the hot and thinner in the cold.

 

[brandoro]

+1 soot.
Diesels are like that. When you change the oil and filter then run the engine for a couple of minutes to check for leaks then check the oil to see if it needs to be topped up it will already be dark.
3 quarts of oil is a lot relative to the engines displacement. As I recall most 300+cu in V8 engines held 4-5 quarts of oil. How many cu in is your tractor engine?

 

[foggy1111]

A long time ago (seems like another life-time) I used to work as a tech sales manager for a laboratory that did used oil analysis. We would routinely analyze the wear particles and contaminates in aircraft, construction machinery, big diesel engines (gennys) and such.

In short....oil does not easily "break down". Rather as said above it becomes contaminated with fuel soot, silcone (dust & dirt), metal wear particles (copper, chromium, iron, lead, etc) and can become diluted with unburned fuel. It is also possible to accumulate moisture and / or anti-freeze from leaks.

We could oftentimes forecast a failure by monitoring the wear metals.....ie "your bearings are going out" (lead / copper)....or "re-check your air filter" etc. This was a new technology when I was involved with it....and there were a few nay-sayer mechanics that later became "believers" after a call from us.

 

[WH401]

As most have said, the reason behind a black-er oil in a diesel engine is because of the soot. It doesn't necessarily mean that the oil is bad, or should be changed, some engines just dump more soot then others. As odd as it is, in the 04.5 - 07 5.9 Cummins diesel's that are in Dodge 3/4 & 1-ton trucks, the oil instantly turns black right after you change the oil. This is because of the 3rd injection event per stroke that creates excess soot particles. The oil is so black you could seal asphalt with it. But, even though the oil is that dark though, the normal oil change interval on that engine is 15,000 miles, and severe service is 7,500.

 

[Wacky]

Is the soot from unburned fuel?

 

[WH401]

No, it's from the combustion process. Large amounts of unburned fuel shouldn't be getting past the rings unless you've got a leaking injector, or similar problem. There is usually very, very slight fuel contamination in diesel oil over the period that it's run, less than 1% total, which is nothing to worry about.

 

[DEWFPO]

I think your GC2610 has a 1 liter, 3 cylinder Iseki engine. That's 3 qts of oil to only ~65 cubic inches.

DEWFPO

 

[RalphVa]

My 4010 only takes 2 quarts.

I'd change the oil on our 1983 240D, and it'd almost immediately be as black as when I changed it, and that oil got VERY black! The oil in my 4010 has never gotten this black, YET.

Our new VW TDI has almost 7,000 miles on it. The oil is starting to get a bit black. Not supposed to change it until one year or 10k miles. First 3 years of maintenance is free. Think I'll shortly rotate the tires tough. Don't think the dealer will clean up the insides of the tires and wheels the way I like to do it when I rotate them.

Ralph