Your bike has a wet clutch, a heavy duty diesel most certainly does not.
I would dare to say that this is the primary reason why we are using motorcycle specific oils in our bikes, not plain motor oil.
Go get a proper oil with the correct additives for wet clutches and drain that heavy duty diesel oil asap.
That said... The rotella t probably won't damage your engine and should be safe to run but it is definitively causing your clutch issues.
The main issue with using non motorcycle oils is that automotive oils have modifiers (zinc) that are good for engines and bad for wet clutches on motorcycles. This is also true for synthetic oils.
Rotella T does not contain the modifiers.
I use it with no issues on clutch slip.
Clutch slip is easy to check for: full throttle in high gear during your bikes powerband. If you hear (or see) bikes rpm increasing significantly faster than speed, then you clutch is slipping.
Clutch slip is progressive, so you would first notice it at top gear with two up riding. Continued riding will eventually cause you to notice with one up top gear riding. Eventually, you will notice the same down a gear, and then during hard acceleration through your gears.
The wrong type of oil causes clutch slip without the progressive aspect. You will notice clutch slip accelerating through the gears within 50 to 100 miles of the oil change. According to my reading, switching to non modified oil will eventually wash out enough of the zinc to allow the wet clutch to work well again.
On the topic of "feels like less decel breaking after the oil change", my only comment is that decel braking is a relative thing. On my bike, if I blip the throttle too much on a downshift, I get a jump forward, before any kind of decel effect. (VMax likes to go, not stop). Point is, decel is relative and not a good indicator of clutch slip.
Hope this helps!
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