Hello CP!
I drive a gorgeous

white 1989 Honda Civic DX 4-door sedan. It has 185000 km on it.
In the summer, in the city, I usually get ~450 km from a 35 litre fill. Which works out to 7.78 litres/100 km. This winter, in the city, my mileage has gotten significantly worse, dropping well off to 11.67 litres/100 km or ~300 km from a 35 litre fill.
I was wondering if, in the opinion of my fellow CPers, I should talk to my mechanic about this or if it is probably normal.
Thanks in advance.