What could be the possible reason for my 2005 focus 1.8tdci to be spending so much fuel? Cold weather aside, i had this problem even in the hotter days but cant come to a solution. Fuel consumption is around 8-9l/100km (around 28mpg) with avg speed at about 60kmh (40mph)

How is your coolant temp? Is the thermostat doing it's job and keeping the engine warm at speed?

Have you tried checking for DTCs with something like Forscan? Something that will read all Ford codes, not just generic ones.

Well it has some problems getting hot sometimes, it rarely gets to 80-90°C (180°F). I need to drive it for almost an hour to achieve those temperatures, i dont know if thats normal.. And unfortunalety no, i didnt find someone with proper equipment for that 😕

have you checked to see if any of your brake calipers are binding? (not retracting fully and causing 1 or more wheels to be continually braked)