I found that the Sertao's fuel mileage varied with the temperature. In the summer, I averaged between 3.2 and 3.6 litres per 100kms. In the late fall, it was 3.6 to 4.1 litres per 100kms.
Altogether, I averaged 3.7 for the year. That's pretty good in my books. I must add that I'm pretty easy on the throttle and keep my speeds to less than 120kph.