What should Honda Fit do if its fuel consumption increases after winter?

For the question you asked, there are many factors that lead to high fuel consumption. Because you haven't seen the current car, I can only help you analyze it, such as driving habits (sudden refueling, sudden braking, neutral taxiing, and the speed doesn't match the gear), low tire pressure, inferior oil, ignition system failure, and electronic control system failure. These failures will increase the fuel consumption of the vehicle. Secondly, if the vehicle is not maintained on time, such as not replacing the air filter, gasoline filter, spark plug and clutch plate in time, it will also lead to an increase in fuel consumption. Then there are carbon deposits and faults in the electronic control system, such as carbon deposits in throttle body, idle valve and fuel injector, and inaccurate signals of oxygen sensor, air flowmeter and water temperature sensor. These will affect the fuel consumption of vehicles. If the fuel consumption is too high, a comprehensive inspection is needed. I suggest you focus on checking whether the signals of all sensors are normal, whether the carbon deposition of all components is serious, and whether there is any problem with the added engine oil. Besides, your car has run more than 80 thousand kilometers, so it's time for a comprehensive inspection. I hope my answer is helpful to you.