A6 Fuel Consumption

[IanBrown41]

Hi all. I have an 2003 A6 1.9 TDI. Temperature gauge stopped working and fuel consumption went from 40 MPG to 27 MPG. I renewed the temperature sender and the thermostat. Temperature gauge now working and fuel consumption has gone up to 31 MPG but not back to where it was. Has anyone got any ideas of anything that could be affecting it please. Could the fuel temperature sender affect the MPG?
Thanks for any help. Ian.