What Are the Reasons for High Car Fuel Consumption?

[CaliMarie]

There are 4 main reasons for high car fuel consumption: 1. Insufficient tire pressure or severe tire wear: Tires are relatively easy to check, so they should be inspected first. If the tire pressure is insufficient, fuel consumption will increase; if the tire pressure is normal, then check the degree of tire wear. When tires are severely worn, they often show signs of slipping, which also increases fuel consumption. 2. Excessive carbon buildup in the car engine: This can lead to higher fuel consumption, and this situation is likely caused by using substandard fuel. 3. Damage to the oxygen sensor in the internal control unit: The oxygen sensor mainly monitors the fuel-air ratio in the engine. Once it is damaged, it will cause an imbalance in the fuel-air ratio, inevitably leading to abnormally high fuel consumption. 4. Malfunction of a certain engine control unit: If one of the control units fails, it is highly likely to cause increased fuel consumption, accompanied by poor power performance and thick black exhaust emissions.

[VonAliyah]

Last time I noticed a sudden increase in my car's fuel consumption, it turned out the tires were underinflated. Driving with low tire pressure is like running in soft-soled shoes—it's extra effort. Running the AC at full blast for long periods also consumes more fuel, especially in traffic when the compressor keeps cycling. A trunk packed with toolboxes and water bottles is like carrying an extra passenger. Keeping your foot on the brake at red lights forces the transmission to work harder. Driving on the highway with windows down creates frighteningly high wind resistance. These are small habits we often overlook, but correcting them can save nearly half a tank of fuel each month.

[SanSimon]

Lao Zhang's car has been burning 2 extra liters of fuel per 100 kilometers recently. I spent half a day helping him troubleshoot. First, we checked the air filter - it was clogged with willow catkins and dust, restricting airflow and forcing the engine to guzzle more fuel. Then we inspected the oxygen sensor, which hadn't been replaced in six years, causing inaccurate exhaust readings. The spark plug electrodes were completely worn down, making ignition laborious. The most critical issue was the deteriorated fuel tank cap seal - gasoline fumes were leaking everywhere, triggering an evaporative control valve fault code. These components should be inspected and replaced every seven years or so, yet many owners only remember to change the oil and three filters.

[VanSavannah]

Why is my new car's fuel consumption higher than the official data? Don't rush to argue with the dealership. During the break-in period, parts have greater friction and the engine oil is thicker. Short commutes are the worst – each cold start uses three times the normal fuel injection, and you arrive before the engine reaches operating temperature. Frequent auto start-stop activation can actually increase fuel consumption. Don't slack on tire pressure – fill them to the door label specifications; 265-width tires consume half a liter more per month than 225-width. Bigger rims look cool but increase rolling resistance and unsprung weight. These details are things dealerships won't proactively tell you.

[DiEva]

The most extreme case I've seen during recent repairs: the owner complained about a sudden surge in fuel consumption, and we found a series of issues. The fuel injectors were clogged with gum deposits, atomizing fuel like a sprinkler truck. The carbon canister purge valve was stuck, allowing gasoline vapors from the fuel tank to flood directly into the intake manifold. The most critical problem was a faulty thermostat, causing the engine to constantly operate at low temperatures while the ECU desperately enriched the air-fuel mixture. The rear wheel brake calipers were rusted shut, essentially driving with the parking brake engaged. None of these faults would trigger the check engine light, but they could stealthily consume an extra 3 liters per 100km - only detectable by reading live data streams with a diagnostic scanner.