Kubota Engine Oil

[trbeau]

I have a 2005 Kubota Beta Marine 38.5 horsepower diesel engine in my Albin 25D.
The original operator's manual states, "A good quality 15W/40 multigrade oil as used in most car engines will meet these requirements. Do not use Turbo Diesel Oil or additives."
The newest version of Beta Marine's manual from Beta Marine's website states, "Do not use lubricating additives and/or fully synthetic lubricating oil." Manual goes on to say, "NB: An acceptable alternative is a mineral based semi-synthetic lubricating oil with a content mix no greater than 30% being synthetic based."
I have used synthetic oil in cars, trucks, motorcycles, portable power equipment, tractors and other boats. This is a new one on me. Maybe when the motor was manufactured they might have restricted use of synthetic oils...but today? In their current manuals?
I stand ready to swap out the Mobil One 15W-40 for Rotella T4 15W-40 but I would love to know WHY Kubota stubbornly continues to publish this strongly worded recommendation. Am I missing something after 30+ years in automotive service and 25+ years of automotive instruction?
Thanks in advance.

[WillieC]

Are you familiar with activeboard?
https://82353.activeboard.com/t61644015 ... brication/

[trbeau]

Yes, thanks, I had read activeboard thread.
Just looking for some definitive engineering explanation where it doesn't appear to exist.