You know the thing with diesels is when someone says "oh meree garee 10 daitee hai, taeraa 8 kioun kartee hai?"
The fact is, diesels can be calibrated to use as little fuel as possible and much as you will be refuelling every 100kms.
My car gives me a fuel average of 6.75 KM/L in the city (Keep in mind its a 2.8 TD) with 32 inch tires. Factory/OEM tires should about 29-30inches. The engine is in its mid life. On Highways it averages out in between 8-10KM/L depending how fast i am going and how many revs im pushing.
The matter of fact is no Turbo diesel is going to give you anything near to a 10KM/L highway and local combined.
Naturally aspirated engines are best for fuel economy and are much more reliable, most all cheaper the maintain.
Get a 80 Series land cruiser with 1HZ 4.2 Liter Diesel engine or a Nissan Patrol with a 4.2 TD42. Best fuel economy and brilliant cars for your price range. Best of all, rarely they break down contrary to Turbo Diesels which require an extended amount of maintenance just to keep it on the road.