Why does my 2014 Honda City only run about 400 kilometers on a full tank of fuel?

My car's horsepower might be over 300, perhaps it's just getting old.

Your estimated fuel cost is over 0.5 RMB per kilometer, which is indeed a bit high on fuel consumption.

In the city, it's over 400 kilometers, which is normal. On the highway, it's about 580 kilometers.