Nisan Pathfinder economy

I have a 2007 Pathfinder, 2.5L, type R51, turbo-diesel. It tows
a 19. ft, 2200kg-loaded, full-height Paramount caravan.

I love the car
— torque is great, power is very good but fuel economy is poor. I recently had the car serviced by Nissan and during a trip from Port Fairy to Geelong (with no wind to speak of and flat terrain) I averaged 21.5 L/100 km.

The fuel economy surely has to be better. Does anyone out there have a similar setup with better economy?

Woud appreciate any comments.

John, Victoria.