A final answer from Kubota on CJ-4 spec

[brucew44guns]

Kubota finally sent me their answer on why CJ-4 oil was not recommended for their engines of less than 50 horsepower. (remember that CJ-4 will include any of the excellent brands of synthetic product you may want to use, none will be CI-4 now, but CJ-4 only).
They say---that if the engine has the exhaust "after treatment" filtration system on it, then CJ-4 is the right choice. But in the case of the ZD331 mower, a 31 horsepower diesel, that has no "after treatment", then the CJ-4 product would cause "crankcase residue build-up" and shorten engine life.
Chevron and Mobil tech services were baffled about this when I called them, and Mobil in particular recommended the Delvac 5-40 synthetic oil that would be CJ-4. Maybe Kubota has 3 boatloads of CI-4 laying around in bulk and need to peddle that to folks like me. It does not make me want to buy a new Kubota tractor next year. Using low sulfer diesel, in a 31 horsepower mower, it makes no sense to me that Chevron, Mobil, Shell, or any number of CJ-4 products would not be totally acceptable in this application.


(a little later after posting this) OK, I called Conoco, read them Kubotas answer on the CJ-4. They said that Kubota was "covering their butt" on this, that the machines might be used in the parts of the world that might still have high sulfur diesel, as has been discussed here. The tech rep told me to use CJ-4, synthetic or otherwise, and not worry a bit. He mentioned that Kubota needed to revise their owners book, and perhaps get their own reps clued in a bit better about oil specs. He said their insistence on CI-4 was not valid, to use the newer spec and not worry a bit. Issue resolved in my mind. Thanks for putting up with me on this question.

 

[Ford850]

Thanks for following up with both Kubota and the oil manufacturers on this. This helps clarify the Kubota logic (valid or not) and we can stop speculating. I will now use Rotella T6 in my Grasshopper mower (Kubota diesel) with no worries at all.

 

[art]

Oil, the long and short from forty plus years of watching repairs. I've seen Kubotas go over 900 hours without an oil change and still no engine failure. I've seen others as well go close to that although that one was most recent abuse.

Kubota has there tractors, the oil companies you called have their oil!!! They both have something to sell!!!

Will a good oil help to extend the life of an engine, with proper changes!
Will a cheap oil hurt the life of an engine, I've seen the results of that too!!

Will the average consumer have an engine failure from cheap oil? I'd doubt it!
The average consumer will never wear out the equipment they buy new. They will replace it before they get to that point of a failure.

Tractor engines that are out there today of quality normally exceed ten to fifteen thousand hours. The other side is four thousand to five thousand hours.

Does the oil make a difference, yes will you see the difference, maybe in fuel economy but nothing until you take an engine apart.

It is amazing that the new engines in tier four run so clean. We are working with them now for knowledge of the new systems. An interesting note on this that for an ag tractor to run in a major city will take in dirtier air then the exhausts will emit!!!!

Kubota is a world wide company and they do have a lot of variations from one piece of land to the next.

I'd tell you to run what ever oil you want, it's your right!

Otherwise we need more work!

 

[daman1]

What a load of crap!

that engine will out live you on CJ4,with todays ULSD thats all thats needed.

CI OR CJ4 WILL WORK!!!...CI is getting very hard to find also.

 

[Chilly807]

The "crankcase deposit" answer may have some validity. Some oils are designed to hold carbon and particulates of whatever kind in suspension, others aren't.

The reason I say this is I've seen the results of some of the "suspension" type oils, and I'm not impressed. The oil formed a jelly like coating over the engine crankcase and rocker covers. An engine oil centrifuge didn't remove the carbon as it should have, and the filter didn't cope well with it either. A different style engine had no problems whatsoever.

We do oil changes based on sample testing, and the change intervals in the first example were much more frequent than previously experienced.

The oil in question is a product called OMD-113, European origin I believe. Whether it is CJ-4 rated or not, I don't know. I don't think it was intended for the small engine market.

Anyway, my point is, I think Kubota was being conservative in not endorsing CJ-4 until it had been on the market for a while to better evaluate performance in their engines. I know people here have inquired about using CJ-4 in their tractors, and Kubota has given them the green light on an individual basis.

Me, I'm still using the Kubota 10w30 until further notice. I'm sure others will disagree and try to save me from my ways..

Sean