Fuel Grade (Page 47)
Your Triumph engine is designed to use unleaded fuel and will give optimum performance if the correct grade of fuel is used. Always use unleaded fuel with a minimum octane rating of 91 RON.
From the RON to US Octane Rating Conversion Chart:
What is 87 octane in RON?
The good news is that at its most basic level, regular gas is regular gas, and 91 RON in Germany is equivalent to 87 AKI in the United States. Premium is the same, and while premium gasoline is often called “super” by some retailers, 95 RON in Germany is equivalent to 91 AKI in the USA and Canada.
My spin: For those that want to use higher octanes in their machine because the fuel has more detergent and the internals stay cleaner, that is not a problem. The manual says OPTIMUM performance is at MINIMUM 91 RON (87 Octane). So any higher grade fuel is for your own peace of mind and has nothing to do with engine performance. The only way to get poor engine performance from gasoline is to use LESS THAN 87 Octane (91 RON). So push whatever pump button suits you, it has NO effect on how many ponies are at the rear wheel.