re-read the zzr thread and it actually said dont use CAR synthetic oil because of the wet clutch- bike synthetic oil should be ok
I used to top up my CX500 and Gt 550 with car type oil when they used it but always tried to get bike specific oil for changes - one of the GT's I had and the CX had a thirst for oil so it didnt do any harm - the Gt 750 and the other GT 550 I have had never used any oil, nor has my ZZR .
After 29 years of biking i can only positively say i've only ever had one issue with a particular oil, and that was after using Castrol Magnatec.
The ad campaign at the time was pretty impressive, but after a weeks usage i just knew something wasn't quite right, and gear changing became a bit of a chore.
It was only then that i had a butchers at the container, and it really did blatantly say, albeit in small writing, "not suitable for motorcycles".
I would've known by now if there was any problems with fully synthetic oil in my bike, bearing in mind i am totally sensitive to the slightest noise change, squeak, heat change or anything whatsoever to be truthful.
All i know is, as previously mentioned by someone else, is that my gear changing is "silky smooth".
If "silky smooth" gear changing is classed as an issue then i'm perfectly happy to put up with this terrible situation. I can only imagine it being like filling your house with £50million of Lottery winning bank notes then complaining that you keep tripping over them, or Hugh Hefner tripping over nipples.