Fuel range GU 2010

[threedogs]

My 2009 CRD is typically at over 13L/100Km and when I tow my 1500Kg offroad van, I'm seeing around 18L/100Km
I don't think these are normal consumption figures. They are a fair bit higher than my previous two Patrols.
What is the most likely cause?

what tyre pressures do you run in your camper 18/100 seems way too high.
I would think 15/100 would be more like it