I read an article recently claiming that using E5 gave better fuel consumption figures, so I gave it a (not very scientific) go. On my modern Honda I improved tank range by about 40 miles on a non-motorway journey (2 up, fully loaded), getting over 70 mpg as opposed to mid 60s. This is on a booster plug equipped bike. Even motorway journeys stayed in the 60s on E5. Of course, price plays a part but it looks like it may be worth it if buying from supermarkets. Not applicable to my S3 'cos I only use super 97/98/99 E5.
I’ve never put E10 in any of my bikes, we don’t have it here in NI yet. When I went for a trip to England in the summer I had to ride around a bit one night to find a pump selling E5 before I could fill up again. I used a website to find one in the end because the first 2 or 3 places I went didn’t have any E5.
Even comparing E5s with different octane I get more miles per tank on 97 or 99 compared to 95.
I read an article where someone had recorded their fuel usage on E10 and then E5. Ethanol doesn’t burn as well as petrol so he found a % improvement and better tank range. The corresponding price increase for the E5 (over E10) was a lower % increase so his “pence per mile” dropped on E5.
That was good enough for me…, I’ve used E5 ever since. I managed over 200 miles on a tank on my 1400 
, having previously run out at 173 and 183…
I read this (older) post with interest, as I have just completed an E5/10 fuel trial with my company car, over a period of the last 12 months.
First 6m with E10 (37.8mpg), next 6m with E5 (44.2mpg).
Rough calcs suggest E5 between 6-9% more expensive, however gain of ~15% more mpg. Crude calcs, but will be sticking with E5 from now on.
For the V1200 Sport, always E5 premium brand…obviously! 
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Thanks for that. It’s rare to get some objective numbers! The difference in mpg between the two grades is surprisingly large. I might do my own test on the V85TT.
I read of someone having done the sums on their bike and that was good enough for me to go E5 Super-Unleaded ever since!! V11 Le Mans and a California 1400 Custom. In particular, the extra mpg gives me an increased range so I can ride to my brother’s and fill up at the local Asda rather than have to stop on the Motorway and fill up at their prices!! 
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My Breva kacked up on that E10 rubbish in Europe, misfiring and spluttering like a bantam
I then filled it with E5 when I got home, and nailed it through the gears before I took it to Tony Botto for its service
fault cured
E10 is kack
so I use either 5 or superpower stuff
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6 miles???
6 months each
Or maybe meters, metric you know lol
Not wrong…