Why is my car's fuel consumption getting higher and higher?

[Ian]

The reasons for increasing car fuel consumption are as follows: Dirty engine oil: When engine oil becomes dirty, it leads to poor lubrication, increasing resistance in various moving parts of the engine. More energy is required to overcome this resistance, resulting in higher fuel consumption. Dirty air filter: A dirty air filter causes poor air intake. Firstly, more energy is consumed during air intake. Secondly, insufficient air intake leads to incomplete combustion, where some gasoline isn't fully burned and gets expelled. Naturally, more gasoline is required to travel the same distance. Spark plugs reaching end of life: Spark plugs are often overlooked, with some people not replacing them even after 100,000 kilometers. Although spark plugs can still function after their lifespan, insufficient ignition energy causes delayed ignition, missing the optimal ignition timing. This also leads to incomplete combustion, further increasing fuel consumption. Excessive carbon buildup in the vehicle: Carbon deposits typically accumulate in the throttle body, fuel injectors, intake manifold, and piston tops. Excessive carbon buildup in any of these areas will cause incomplete combustion, thereby increasing fuel consumption.