Hmmmnmm, In the last 6 months I stopped buying premium gas for my S4RS and Paul Smart 1000DS and only buy the 87 stuff. The Ducati engine is not really built as a high compression engine. High compression is the reason for high octane. The higher the octane, the more stuff they put in there to prevent pre-detonation. This actually translates to less gas. It's a fractional amount, but engines work on incremental, almost immeasurable changes. We've all commented on how well our engines run in cool weather, that tiny change amounts to HP we can feel.
So there you have the flipside. From a guy that bought only premium for at least 10 years for his motorbikes. I still buy premium for my Norton, but that's because I built the engine myself and know it has the higher compression Combat head. I've actually found tiny improvements in switching over to lower grade, mainly in my wallet.
09 Aprilia RS125 plated
06 Paul Smart Sport Classic NFS ever.
08 S4RS Tricolore #081 NFS ever.
01 M600, aka, The Pink Monster
97 900SS CR
72 Norton Commando 750
03 KX60 with S4R rear shock,Honda CB350F, Hodaka Ace90, 3x Yam-YGS1, Yam-CS3 200, Vespa small frame, Gilera 106, Puch Sabre, Puch 50 Boy Racer, Benelli 250, Benelli 360, Honda CB350T, and many more.