KUBOTA BLACK ENGINE OIL QUESTION

[MULESKINNER]

Why do all of my Kubota tractors turn the engine oil black with soot in about one hour of operation? I purchased the machines new and change the oil and filter every 50 hours. My Cummins powered Dodge P/U goes about 1000 miles after I change the oil before it starts to turn black.

I believe it's because the Kubota uses an "Indirect injection" engine, where the Cummins uses a "Direct injection" engine.

What say you?

 

[Lance]

It's a diesel thing, my DI VW blackens the oil right away.

 

[ABULL4U]

I have noticed the same issue with my Kubota ZD-28F ZTR mower in comparison to my John Deere 955 with a Yanmar VTN-84. Both bought new and oil changed more frquently than recommended by the factory. Maybe possibly an emissions related cause?

 

[JR]

It is a diesel thing. I have a Kubota RTV-900R that was bought know, use M1 0W-40, now has 600 hours. It turns the oil black within just a few hours of operation. I have known several people that own 6.2 and 6.5 litre GM diesels and many others with 6.9 and 7.3 litre Ford diesels. I have changed oil on several occasions and all have turned the oil black immidiatly. I mean I fill the crank and check the level and it is dark. Then you start it and oil pressure it up to check for leaks and the oil instantly turns the oil black as can be. I have experienced the same thing with an older yammar diesel powered generator that I own. I do not know how many hours is on it. I ussually use what ever HDEO 15W-40 I have on hand for it. I hope this helps.
KC

 

[Ray H]

It's a soot thing (unburned and partially oxidized fuel insolubles - the reason HDEOs are loaded with detergent/dispersants) - most goes out the exhaust, but some gets blown past the rings into the oil. Diesels spew out soot particulates wholesale which is why there are virtually no diesel automotive sales in California anymore. Increasingly looks like diesel light and heavy trucks, locomotives, and emergency generators are on the list in this state for particulate traps. The only question is whether the legislature will require backfitting existing engines.

 

[GregH]

My results are just he opposite. My 4310 GST has over 550 hours and the oil becomes black after maybe 60 hours. I do observe several rules. Adequate warmup before using at about 1300 rpm until engine shows some heat via the temp gauge.
No idling to exceed 5 minutes, at least no low idle.
When in use I try to avoid any low rpm use especially in cold weather, which helps keep the engine temp in its more effective range.
I think how we run them to some degree determines the soot load of the oil. In the new computer controlled engines, the fuel management probably helps with that problem somewhat.
Just my 2 cents adjusted for inflation!
GregH

 

[mburnickas]

My little old school Bota BX22 using amsoil looks like honey no matter the hours. Gets (1) year drains like everything else I own.

Same thing when I had my powerchoke...oil looked fine (not black).

My old deere (455) with the yanmar diesel got a little brown but that was it. The JD oil was black after 5 minutes using.

Then again, color does not mean much..