We went on a small trip in February, headed down south for a couple of weeks did 2500km. Crd Nissan patrol normal driving at home 14/100km on the trip we towed our windup offroad camper about 1000kg at 105km/h with the cruise set and returned 17/100. I think I could have gotten that down by not using the cruise and driving a lot gentler, but your on holidays bugger it set the cruise and enjoy the drive.
Shane