Oil color

motionclone

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Ive owned 3 kubota engines now and several other diesels over the years. After an oil change the oil only looks clean for a short time then turns black quickly. This has been my experience up until recently. My new to me 3000hr Bobcat T300 Track Loader with 82hp turbo kubota engine has 30 hrs since last oil change and its still golden new color like a gas engine would be. Anyone have any ideas? Engine is original.

My 1000hr Kubota tractor with 34hp non turbo engine turned the oil black right off.
My 2500hr Kubota powered excavator has 50hp turbo and turns the oil black just as quick.
 

PoTreeBoy

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Ive owned 3 kubota engines now and several other diesels over the years. After an oil change the oil only looks clean for a short time then turns black quickly. This has been my experience up until recently. My new to me 3000hr Bobcat T300 Track Loader with 82hp turbo kubota engine has 30 hrs since last oil change and its still golden new color like a gas engine would be. Anyone have any ideas? Engine is original.

My 1000hr Kubota tractor with 34hp non turbo engine turned the oil black right off.
My 2500hr Kubota powered excavator has 50hp turbo and turns the oil black just as quick.
It's not unusual. My L35 with 2000 hrs kept the oil clean for 20 - 30? hrs just using the FEL to haul brush. But a few weeks ago I used the backhoe pretty hard and the oil turned black in less than six hours.
Our Ford with 600 hours turns it black in just a few hours.
 

mcmxi

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I've found for my F250 7.3L that the type of oil used makes a difference as to how quickly the oil turns black. I haven't tried different oil filters on that truck but that could effect contamination rates. For the same engine, I would expect oil type, oil filter, fuel quality and driving habits (related to combustion) to effect how quickly the oil turns black.

For different engines it's a lot more complicated. The four variables above would apply but you'd have to add in other variables such as piston rings, cylinder walls, injectors, fuel etc.

I have noticed that the oil on both MX6000s stays clean for a "long" time, both the oil that comes in the tractors at delivery and the oil added at the 50 hour service.
 
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mcfarmall

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The detergents in the oil play a factor in how quickly it turns black. Detergents grab hold of soot, etc and keep it in suspension to be trapped in the filter. A good detergent package should turn black or dark fairly quickly.
 
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RalphVa

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Blackest oil was on our 1983 240D Benz that we kept for 25 years. Its oil would turn black almost instantly after a change. Best has been the Isuzu generator driver. Stayed almost crystal clear through the 50 hour change. Now, with 190 hours on the oil change (Castrol 5w30 from VW), it is still not black. Due for its 10 year change this year.

The 3 JDs oil would turn black fairly quickly but not near as black as on the old Benz.
 

mcmxi

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The detergents in the oil play a factor in how quickly it turns black. Detergents grab hold of soot, etc and keep it in suspension to be trapped in the filter. A good detergent package should turn black or dark fairly quickly.
Good point, but I will add that the detergents help to keep important metal parts free of deposits and neutralize acids that form in the oil, but it's the dispersants that keep the contamination dispersed and in suspension. The base number (BN) indicates the amount of detergents in the oil and most values are similar when comparing quality engine oil.

I don't think it's an obvious assertion that if your oil isn't black fairly quickly that the oil isn't doing a good job of cleaning cricital metal parts. You can make the argument that superior engine oils reduce the amount of deposits on critical metal parts and therefore more particulates are exiting via the exhaust.
 

GeoHorn

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The best oils will have good detergents AND good dispersants. It’s the dispersants that keep the junk suspended in the oil so that it drains out with the next oid drain period. Good diesel oil looks dark very soon after oil change. That’s my opinon.
 

B737

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The only diesel oil I've seen that does not turn black almost immediately is the oil in the LX. 50 hours, changed it, still gold, 80 hours still gold. Yet all the other diesels in my life; boat engines, truck engine, previous tractors, all turn their oil black immediately.
 
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