its' a 18L tank including the reserve - it does about 220 km up to reserve which is about 4.5L so may be I'll just take a 10 litre spare tank which will give me another 200 km .. With extra weight , wind etc the bike will burn more gas.How much mileage do you get out of a full tank? I didn't use any of the spare fuel I brought when I did the JBR. I had close to 3 gallons. But I have a 6 gallon tank. Maybe you don't need to bring so much extra fuel.