Your avatar says 2005 CVT, but....... you say this car is 9 years old which makes it a 2009 model in your question..
By 'semi-automatic' do you mean i-shift gearbox ? If so the gearbox oil should be changed at 70,000 miles ( i-shift is basically a manual gearbox with actuators to change the gears) so it will be Honda MTF or Castrol syntrans ( or any other manual gearbox oil ). For the CVT box the change interval was reduced by Honda to 25,000 miles after problems owners had after leaving it in for longer.
Colder weather will make MPG worse, even if your driving style has not changed, personally after 9 years even if the 70,000 miles has not been reached I would change the gearbox oil, plenty of info on forum how to do it or get your garage to do it..