From the moment you start your car’s engine until you turn it off, you need fuel for almost every operation, including moving and stopping the vehicle. The amount of fuel consumption is important not only to you as the car owner but also serves as an indicator of the overall health of the car and various engine components. Although in some specific conditions, such as parking the car under direct sunlight on hot days, a small amount of fuel may evaporate, this should not mislead you into thinking that the car consumes fuel while stationary. But the question is, how can fuel consumption be measured? What factors influence fuel consumption, and why is fuel usage sometimes higher than usual? In this article, we intend to examine the reasons behind increased fuel consumption.

Notes on Car Fuel Consumption

In many countries around the world, including European countries, China, South Africa, Australia, and Iran, vehicle fuel consumption is measured according to standard methods. This metric refers to the amount of fuel consumed per 100 kilometers driven and varies depending on the type of fuel used (gasoline, diesel, or gas).

Fuel consumption varies based on driving conditions. For example, driving on uninterrupted highways typically results in lower fuel consumption compared to city driving, which involves frequent stops and speed changes. Factors such as traffic congestion, frequent gear changes, and varying speeds all impact the amount of gasoline consumed.

How to Measure Your Car’s Fuel Consumption?

To accurately calculate your car’s fuel consumption, follow these steps in order:

1. Wait until the fuel tank is nearly empty (fuel gauge shows “E”).
2. Note the current reading on your car’s odometer.
3. Refill the fuel tank completely and continue driving as usual.
4. When the fuel runs low again, record the new odometer reading.
5. Subtract the first reading from the second to find the distance traveled.
6. Divide the amount of fuel you added (in liters) by the distance traveled (in kilometers).
7. Multiply the result by 100 to get the fuel consumption per 100 kilometers.

Example: Suppose your odometer reads 128 km initially, and after refilling 22 liters of fuel, it reads 428 km. The distance traveled is 300 km. Dividing 22 liters by 300 km gives 0.073 liters per km. Multiply this by 100 and you get 7.3 liters per 100 km. So, your car’s fuel consumption is 7.3 liters per 100 kilometers.

What is Combined Fuel Consumption?

As mentioned, fuel consumption varies depending on driving conditions. To get a more accurate assessment, an average fuel consumption is calculated over different driving situations:

• Driving in heavy traffic days
• Driving on highways outside the city
• Driving within the city

The average of fuel consumption across these conditions is known as the combined fuel consumption.

Reasons for Increased Fuel Consumption + Important Tips!

You might be among those who worry about the sudden rise in your car’s fuel consumption. Here are some common reasons for increased gasoline use and ways to reduce it:

1. Cold Weather and Use of Tire Chains: In cold seasons, fuel consumption can increase by up to 10%. This is due to the engine requiring more energy to start in cold weather and increased friction caused by tire chains and winter tires. Additionally, low tire pressure and use of the heater also affect fuel consumption.
2. Improper Engine Tuning: If your car’s fuel consumption has increased abnormally, the engine may need tuning. Problems in various engine parts and combustion chamber can raise fuel use. Fixing technical issues and tuning the engine can help reduce fuel consumption.
3. Driving at High Speeds: High-speed driving is a major cause of increased fuel consumption. For every 8 km/h increase in speed, fuel consumption rises about 7-8%. Generally, suitable highway speeds range between 70 and 90 km/h.
4. Not Turning Off the Engine During Long Stops: If you plan to stop for a long time, it’s better to turn off the engine. Idling for long periods is a key factor in higher fuel consumption. Some modern cars have Stop-Start systems that automatically turn off the engine when stopped.
5. Misaligned Steering Wheel: An unaligned steering wheel not only causes handling issues but can increase fuel consumption by up to 10%. Rough roads and potholes may cause steering misalignment. Proper alignment reduces fuel use and ensures passenger safety.
6. Sudden Braking and Acceleration: Abrupt braking or accelerating shocks the engine and increases fuel consumption. To save fuel, avoid rapid speed changes and use cruise control if possible.
7. Issues with the Fuel Cap: A faulty or missing fuel cap increases fuel consumption and releases gasoline vapors into the air, harming the environment. Always check the cap after refueling; a loose or damaged cap may trigger the check engine light.
8. Carrying Heavy Loads or Unnecessary Items: Every extra 45 kg in the car increases fuel consumption by 1-2%. Keeping your car lighter optimizes fuel use. Remove unnecessary items and carry only what you need.
9. Using Incorrect Engine Oil: Wrong type or incorrect quantity of engine oil can raise fuel consumption. Always use oil recommended for your vehicle and check levels carefully.
10. Keeping Your Foot on the Brake Pedal: Habitually holding the brake pedal while stopped can increase fuel consumption by about 35%. It also causes brake wear. Best practice is to shift to neutral and engage the handbrake when stopped.
11. Lowering Windows at High Speeds: Driving over 80 km/h with windows down worsens aerodynamics, increasing resistance and fuel use. Use air conditioning in recirculation mode and avoid unnecessary use to save fuel.
12. Not Changing Air Filter on Time: A clogged air filter forces the engine to work harder, increasing fuel consumption. Replace the air filter as recommended in your owner’s manual.
13. Driving on Sandy or Dirt Roads: Driving on uneven, sandy, or dirt roads increases fuel consumption by about 30% compared to paved roads.
14. Incorrect Tire Pressure: Improper tire pressure is a main cause of higher fuel use. The recommended pressure is usually on a sticker inside the car door. In winter, slightly lower pressure improves traction but increases consumption. Underinflated or worn tires also reduce braking efficiency.
15. Skipping Regular Vehicle Maintenance: Routine servicing helps detect and fix issues such as suspension problems that raise fuel use. Regular maintenance keeps your car running efficiently.
16. Excessive Use of Car Accessories: Frequent use of features like seat warmers and other electrical systems, especially when unnecessary, increases fuel consumption since they draw energy from the engine.