I bought a new XT660R in 2014 in Perth Australia. On the stock 15 litre tank, I rode to "Wave Rock" on one tank, that is 350km, and 23 km/litre. As this was a run in, I kept the speed low. I would later ride harder, but never got less than 300km/tank.

I also have a GS1200BMW, so weight is never an issue on the XT, it feels like a bycycle in comparrison. Due to distances in Australia, and also the arbitrary availability of fuel, I installed a 26 litre tank from "Off-The-Road" as well as a 2-1 Pipe and acropovic plus a Power commander.

The standard bike has a bit of a surge, but it was really the clearance and the weight that made me buy the 2-1. Saved 12 kg's and added some KW's. From stock 35 on engine, to 48 on a dyno. The bike moves like a rocket!

Best of all, I never fill up before 500km per tank, and has filled up after 600 km more than once. Riding in Australia at 100km/h, I often got 24 km/l.

Now in South Africa, I travel way faster, at 140 km/h, and still gets 20+km/l.

Im so happy with my XT, I sold my GS1200 last weekend. I may buy a GS again, but it seem a little pointless. I would rather take my XT RTW than the colossus. If only Yamaha had the same customer service tan BMW.

I have spoken to XT riders and reads whatever I can. Indeed, there are encyclopedia's written on mods you can do on these bikes, but a stock bike can take you RTW also.

that's really nothing yet, look here 100k miles!:

https://www.youtube.com/watch?v=Isa5aBsoa9U


I do as well over 500km on the tank no problem.