Hi ,
I have been using Xterra for pastv2 years and done about 60 k km . The first impression is that the X is very capable both on Road and off, the best you can squeeze out the tank is close to 600 with just 2 liters to spare ... but I drive very prudently and always use the overdrive on the gear selector to achieve better range . Don't abruptly speed up or stop - basics of driving will get you close to the range of 525 to 575. The minimum is to get a good radiator skid plate as the radiator is below the chassis. Other than that just drive it and enjoy....
Drive ride safe,
Slick72
NB: Am known as the K Man( Kanjoos Man🙄🙄😁😁 ) for squeezing the max range for given fuel