The following is extracted directly from my owner's manual concerning oil specification*:
"API Service Classification SG or higher except oils labeled as energy conserving or resource conserving on the circular API service label, SAE 10W30, JASO T 903 standard MA, Pro Honda GN4 4-stroke oil (USA & Canada) or Honda 4-stroke oil, or an equivalent motorcycle oil."
So it's all a little confusing to me. I totally get that there are different organizations in different areas of the world; European, Japanese, and North American that have different classification systems. The North American system is API and that's where we get the requirement for at least SG and not having "energy conserving" or "resource conserving" on the label and any engine oil at or above this level is approved. The Japanese classification JASO is where the JASO T 903 MA comes from. And the European standard ACEA but that spec is not addressed in my manual, but it is the two other classifications beyond API that make me not want to use an engine oil designed specifically for meeting clean diesel specs.
Issue 1: It looks like to me, that even though API is fine with Rotella T5 10W30 for my bike (SM and no energy conserving or resource conserving on the label), as far as I can tell, both ACEA E9 and JASO DH-2 approval level does not approve this oil for my bike, as those are both commercial, heavy-duty engine specs only and do not address suitability for a motorcycle dual lubing necessity.
The second thing that would bother me personally using a high-quality diesel oil is that there is a lot of engineering work and time that went in to developing this oil specifically for it to do a good job protecting a diesel engine and the environment from modern, high pressure, compression-ignition combustion and engine-out exhaust, e.g., its ability to absorb high amounts of soot, fuel dumping into the oil, compatibility with DPFs, etc. I'd be leaning towards the idea that a very good engine oil for compression ignition is not necessarily the best choice for a motorcycle or even a gas-powered car no matter the quality level of the oil for a compression-ignition engine.
I'm not trying to debate or prove a point. I don't know. The T5 advocate likely knows much more than me. I just don't have enough understanding personally to feel confident using anything but an mc-specfic oil and I look for the MA JASO spec and at least SG and either 10W30 or 10W40. My MC is not very oil picky and it is somewhat low revving and I don't run it hard, so it probably wouldn't make much difference as long as it shifted okay, but to be on the safe side, I'm sticking with what I understand about the labels.
* My manual specifies the same engine oil for the standard shift and the DCT automatic version, even though the DCT actually has transmission fluid as a separate lubricant.