Certainly for diesel, and maybe so for petrol,
I used to run a bog standard soot burner with boggo supermarket diesel & two shots of Miller cetane booster,
you are confusing matters by assigning definitions that are wrong - assuming you are referring to the UK, super unleaded has to be at least 97 RON. Fuel sold as premium unleaded is bog standard unleaded at 95 RON. Some branded premium fuels such as Tesco Momentum claim 99 RON. Shell V Power claims to be 4% superior fuel but does not claim a particular RON. It has dynaflex whatever the fuck that might be. Note, these premium fuels do not claim to be super unleaded as I guess they do not want to be associated with the 97 RON super stuff sold by Sainsbury's.
Anyway, keep buying the posh petrol. It's not likely to be any better for the GS but it will make you feel better and redistribute more of your money to HMRC.
67000 mile on gs in 4 half years , 100,000 in 6 years on r1100rsse waffle waffle let me guess small d**kwaffle waffle . unleaded for a start uses ethanol which is lest potent than petrol which results in less emissions and power , I take a stab at this guess you have a gsa with low suspension or a rs with a tank bag .
I read in my r1200Gsa Handbook to use (E5) Super unleaded, that's okay in most major cities, where garage forecourt choices are plentiful, but as soon as venturing North into the NC 500 areas, all that is diminished as
Tesco's super unleaded is 99 RONA brief window of opportunity turned up around 2020 when Shell and Esso finally made a UK fuel that met the requirements for the twin cam R1200's and the K1300's - all of which should be fed >98 Octane fuels - before that the highest available was 97, and its not enough to trip the 2010 to 2013 bikes on to the performance map they are meant to use all the time...
BP have never made one that will work - but their 97 super unleaded is now the best fuel we get - it still smells and runs like petrol - whereas the other two sell something more akin to jazzed up water that does almost nothing
Asda which used to sell one of the lowest ethanol infected fuels do not sell anything other than 95% octane dishwater these days
And no air cooled R1200 was ever meant to run on Ethanol crap fuels (and that's the same situation for the K1300s)