I use a little app called 'fuel use ' that works it out and you can save data as csv file so you can put it into excel.
My bike does about 235 miles to find trip if I ride 80 to 85 on motorways or 240 and up if keeping it to 70 or 75. Easy 300 mile from a tank with 21 to 22 litre refill. I've drilled the filler.
Take out the cat it improves fuel consumption.

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