Mercedes ML320 CDI (W164) reduce fuel consumption?

Hello folks, I bought a (W164) ML320 CDI 224ps, built in 2006, diesel automatic, mileage: 180,000 km. I want to adjust or do something to reduce fuel consumption. How can I reduce fuel consumption? I have read and seen almost everywhere that the consumption is less than mine. My consumption is: Highway: 10.5 liters City:…