Originally Posted by Charles Darwin
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Key point is, a modern bike (built since ~2005 or so) has been engineered to cope with ethanol, no problems.
In this case a small percentage of ethanol is actually beneficial for storage, since it is hydrophilic and will mix with any water in the fuel, eventually escorting it out.
The problems occur in older bikes! Ethanol can be unfriendly to earlier models where the entire fuel system may not be engineered around its presence.
Ethanol is simply a wood alcohol (the kind that makes you go blind/kills you if you drink it).
It is the stuff in the little red bottles, commonly found for decades in gas stations, sold as fuel line anti-freeze.
It will mix with any water in the gasoline, escorting it out, preventing your car freezing up in extreme cold.
Therefore, Shell or Esso 91 are great to use in any older (carbureted) motorcycle.
Many bikes may not require the extra octane per se, but they'll run great (no ethanol).
A newer model could use the 89 containing 5% ethanol for storage.
I think everyone agrees 87 octane (containing up to 10% ethanol) is inappropriate for either riding or storing your bike.
Most bikes require at least 89 octane for performance reasons.
And if it does not, it soon will!
Typically motors, though running fine on regular 87 when new, will benefit from higher octane after accumulating mileage.
Carbon buildup will introduce preignition (detonation) hot-spots, and you may encounter knocking you never had when new.
The manufacturer's octane recommendation is for their brand-new motor...
Again, octane itself has nothing to do with storage.
We here in Canada simply tend to use it as an indicator of how much ethanol the fuel contains, hence the confusion.
Regards
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