I would suggest to watch temp and your radiator fan, because it doesn't have to be that your engine temp wil rise if your fan is running full speed. But that will affect your FE anyway because of more power needed by the alternator to run the current needed.
You'll find some info here
Radiator fan activation temperature
I've connected a red LED with 560ohm resistor in line to see if my fan is kicking in. If the fan is running too much you can open a bit your grille block and let the air to pass it more freely. By trial and error you'll find the best cover size for your grille.