What nonsense did I write!?
Anyway,
advancing the timing will raise the octane requirements. What you're doing is raising the dynamic compression ratio and it will probably knock worse on the 93 RON crap, that's about 87 AKI octane if I remember correctly.
Just a bit of an addition, I've found some newer cars that require regular will run better on Premium.
For example the new 3rd Gen Ford Focus only requires regular 87 AKI octane but it says in the manual that it will run smoother and better on premium. Which also means it
should run a bit better on E85 since the 2012.5+ MY is FFV. But the only guy I know running E85 in a '12 Focus is getting about the same efficiency as Gasohol. Average for the new Focus seems to be around 32 MPG on Fuelly so it's not terrible but he's done 42 or so with Gasoline.
The Honda Fit might be one of those too but I need to verify first.