Your Dodge Journey 2014 SE's fuel efficiency of 8KM/L in the city and 9-9.5KM/L on the highway is below average. Factors affecting efficiency include driving habits, tire condition, and engine health. Regular oil changes and recent air filter replacement are positive steps. Consider checking the fuel injectors, spark plugs, and ensuring the tires are properly inflated. At its age and mileage, it's worthwhile having a mechanic inspect for potential issues like a clogged catalytic converter or oxygen sensor problems. Addressing these could improve fuel efficiency. Overall, consult a professional for a comprehensive diagnosis and advice.