Not so certain I'd rely on any statements of "newer engines have no problems" with it. Some engines in newer scooters (see the order of words there) may not be the newest mostest modernest technology that would enable them to use E15 without issues. It may work out OK, but then it might not. So I'd stick with what Stig stated... go with what the manual says.
But then, it depends what manual you look at for the AK 550. My owner manual says 95 octane. More likely than not that is the Euro RON number (Research Octane Number). In the USA that would translate to about 91 octane (PON or Pump Octane Number). But then the service manual that I downloaded says no less than 90 octane. Since that manual was downloaded from the Austrian Kymco HQ I take that to also mean the Euro RON number... which would translate to the USA 86.5 octane (PON). But the end of the discussion for me is that the sticker on my AK in the storage box (attached) says to use 87 Octane. This sticker was printed for USA models so that's what I put in.
As to using E15... ALL vehicles in the USA that can use E15 or even E85 or any other level of Ethanol more than 10% Ethanol must have a sticker stating that it is allowed. I believe this is by law in the USA for any engine that even has the ability to use E15 or higher. For vehicles that can use E10 or less no sticker is required. There is no sticker on the AK gas door or cap nor is there any information provided in any official manual that I have read that indicates anything more than E10 can be used. There is just no mention of Ethanol indicated anywhere I can find. Yet the dealer and Kymco USA have told me that E10 is fine.
So I would stay away from E15 for the AK 550 until/unless there is new official information that it can be safely used.
BTW- we all know that any scooter with a CVT does not have a neutral GEAR. But there is a lower rpm limit at which the clutch releases so that is what is referred to where it reads "in neutral" on the sticker.
