What Are the Reasons for Excessive Car Fuel Consumption?

[Judith]

Reasons for high car fuel consumption: 1. Tires: Tires are relatively easy to check, so they should be inspected first. If the tire pressure is insufficient, fuel consumption will increase accordingly. 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. Engine: If there is a significant buildup of carbon deposits in the engine over a short period, it can also lead to higher car fuel consumption. This situation is likely caused by the use of substandard fuel. The solution is to add a certain amount of cleaner when refueling. If the effect is not obvious, it indicates a substantial buildup of carbon deposits in the engine, in which case it's best to leave it to a 4S shop or repair shop for the technician to clean the carbon deposits inside the engine. 3. Oxygen Sensor: As an internal control unit of the car, the oxygen sensor primarily monitors the air-fuel ratio of the engine. Once it is damaged, it will cause an imbalance in the engine's air-fuel ratio, inevitably leading to abnormally high fuel consumption. After the oxygen sensor is damaged, the vehicle will emit darker-colored exhaust from the tailpipe during driving. In this case, the oxygen sensor should be replaced as soon as possible. 4. A Certain Engine Control Unit: Although the electronic control unit of the engine is highly reliable, faults are inevitable in vehicles that have been used for a long time. If one of the control units fails, it is likely to cause an increase in fuel consumption, accompanied by poor power performance and thick, black exhaust emissions.

[DiMicah]

That time my fuel consumption suddenly skyrocketed, which scared me into investigating the cause. First, I found all four tires were underinflated - low tire pressure increases rolling resistance, especially noticeable at high speeds. Later during an oil change service, I discovered the air filter was completely clogged and blackened, forcing the engine to work harder and burn more fuel. While cleaning out the trunk, I removed two large boxes of unused tools, and the fuel efficiency improved immediately after reducing weight. Driving habits needed adjustment too - I used to love stomping on the accelerator to overtake, but now I've learned to anticipate road conditions and press the pedal gently. If all these don't help, I'd suggest checking the oxygen sensor, as it directly affects the ECU's fuel injection control. Oh, and yes - running AC in summer does increase fuel consumption by about 10%, but compared to safe driving, that extra fuel cost is nothing.

[OFernando]

My car undergoes regular maintenance, and the fuel consumption has remained quite stable. I always prioritize the condition of the air filter and spark plugs. A dirty air filter reduces intake efficiency by 20%, naturally increasing fuel injection. Spark plugs used for over three years see a decline in ignition efficiency, leading to incomplete combustion and wasted fuel. The engine oil is changed every 8,000 kilometers without fail, as low-quality oil increases engine friction resistance. Tire pressure is checked monthly—a 10% deviation can increase fuel consumption by 3%. Oxygen sensor failures are often overlooked; they send incorrect signals to the ECU, causing the engine to over-inject fuel. Once, after maintenance, abnormal fuel consumption was traced back to an apprentice overfilling the engine oil, where the excessive oil level increased crankshaft operation resistance. In fact, timely basic maintenance can prevent most fuel consumption issues—spending a little to save a lot.

[LaJonathan]

I've noticed that high fuel consumption in older cars is often related to sensors. For example, the oxygen sensor acts like the car's taste buds, monitoring exhaust oxygen levels to adjust the air-fuel mixture. If it fails, the ECU blindly injects more fuel. A clogged catalytic converter restricts exhaust flow, forcing the engine to work harder like running with a mask on. Worn spark plug gaps cause delayed ignition, preventing complete fuel combustion. Carbon buildup on fuel injectors affects atomization, leading to larger fuel droplets and lower combustion efficiency. These issues won't trigger warning lights but cause noticeably increased fuel consumption. Additionally, leaks in the fuel tank ventilation system can allow gasoline vapors to escape - you might smell strong gasoline odors in parking lots when this happens.