High Fuel Consumption Rav 4 Diesel 2007

[GN100]

I have been struggling with high fuel consumption on a Rav 4 Diesel 2007 2.2 D-4D. Mileage run is total 100,000 but only about 20,000 on current engine due to engine replacement under warranty for the known head gasket problem. Over several tankfuls and calculated from full to full, in other words, ignoring the MPG indicator in the car, it returns around 26mpg. Most road tests from owners of used cars seem to indicate that it should return circa 40 mpg. The car has been in and out of the local dealership for the usual filter changes, reprogramming of ECU's, etc, but no solution. I am beginning to suspect by a process of elimination the injectors although I don't think the exhaust emissions are over rich. Any ideas anyone?