Hi
I would think around about 12 or 13 lt/100 with the prado. I've got a 2012 prado diesel and tow a van of around 1800kg and I get Round 12/100 which I am more than happy with.
Good luck with your search.
Ashley
I drive a 2005 Prado 120 - 3ltr diesel (just about the same as yours). In 2011 we did a 13100 km trip (LSL) from West Aust to/through South Aust and back with a 2004 Jayco Expanda (1.5 tonnes). The worst economy was around 19 ltrs per 100km and the best around 14 ltrs per 100km while towing (interestingly about the same stretch of highway but different directions). My average for the trip was 14.9 ltrs per 100kms, but that included a fair amount of bobtail touring.
If you have the time, travel with the wind and around 85 - 95 kph, but if time and weather doesn't permit, expect your fuel usage to go up a little.
Wayne
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My wife says I never listen to her... well I think that's what she said.
I have done several trips from Perth to Collie in the last couple of months as we are moving down there next week, we cut through from Wokalup to Collie, very hilly, towing 17ft van, average on last three trips, 13.94 litres per 100, 13.41 and 12.94, 3 litre turbo diesel.