I am a sales rep with an oil company(not Amsoil) that primarily caters to the diesel markets. First, there has been so much confusion over the CJ-4 spec as compared to CI-4. Kubota's stance on CJ-4 has been to not reccommend it and here's why. Kubota sells tractors all over the world and in many South American markets the sulfer levels in their fuel is astronomically high compared to N. America and elsewhere. Most off-road fuel here in the states has already been dropped to 15ppm just like the on-highway stuff. The only difference is the dye in off-road. Anyway, the higher the sulfer level in fuel, technically the higher TBN number you will require in your oil to combat the acids that are formed when sulfer mixes with condensation in the crankcase. The old CI-4 oils usually had a TBN of around 12. The newer CJ-4 spec oils generally have a TBN of around 10. The reason for the lower TBN is because thanks to the tree-huggers, almost all of the sulfer has been removed from the fuel; hence you do not need as high of a TBN in the oil. CJ-4 oils outperform CI-4 oils in every erea of performance EXCEPT in countries that still use poor quality diesel that has high sulfer in it. I'd take a well-formulated CJ-4 oil over any CI-4 oil with the fuel that we have in the states. CJ-4 oil is far better at handling soot in the oil caused by EGR systems. It also has proven over and over to be better at preventing valvetrain wear and handling high-heat from turbos. Kubota is playing it safe by just not reccommending CJ4 because of the various markets they sell in have different levels of sulfer in it. I have run CJ-4 in all three of my Kubotas and will continue to do so. There are a few companies that offer a high TBN CJ-4 oil to consumers(Amsoil,Texas Refinery are two that come to mind). Starting TBN numbers can be misleading at times because some oils will have a high TBN number when you pour it in but will drop quickly with use. Other oils will have a lower beginning TBN number but do a good job of maintaing the TBN while in use. I do not know of a "bad" CJ-4 oil. Some are better suited to extended drains but if you are going by the factory scheduled service times you can't go wrong with any of the major players. If you shop big-box stores (China-Mart) they routinely put one of the three major players on sale regularly(Delvac,Rotella,Delo) for about $10 a gallon. Using any one of the three will keep your Bota engine running longer than you will be around to see it. Hope this helps answer your concerns.
