How to Calculate Fuel Consumption per 100 Kilometers for a Car?

[CassidyRose]

Fuel consumption per 100 kilometers is equal to the fuel consumption (in liters) divided by the distance traveled (in kilometers) multiplied by 100. The fuel consumption per 100 kilometers indicated in the manuals of domestic cars is generally the constant-speed fuel consumption. Constant-speed fuel consumption refers to the fuel economy indicator when a car is driving at a constant speed on good road surfaces. Several key technologies related to fuel consumption include three main aspects: 1. The relationship between vehicle weight and fuel consumption is directly proportional; for every 10% reduction in vehicle weight, fuel consumption will correspondingly decrease by several percentage points; 2. The car's design—smaller aerodynamic drag on the body will significantly reduce fuel consumption, and the relationship between these two is also directly proportional; 3. Road conditions are an important factor affecting fuel consumption.

[LaJayce]

I always calculate this before every long trip. First, fill up the tank until the pump automatically stops, and note down the mileage A. After driving about 100 kilometers, go back to the same gas station and fill up until the pump stops again, then record the amount of fuel added this time, B (in liters). Divide B by the distance driven and multiply by 100 to get the fuel consumption per 100 kilometers. On my last road trip, my car calculated 8.2L. The fuel consumption calculation app on my phone automatically generates a super intuitive graph, and now it can even display instant fuel consumption. Remember to use the same pump, as different gas stations have different pump pressures which can affect accuracy.

[DanteMarie]

Here's a simple but super accurate method: Wait until the fuel gauge light comes on, drive to the gas station, fill up until the pump automatically stops, then reset the trip meter. Drive normally until the light comes on again and note the distance traveled. For example, if you drove 420 km, record the fuel added this time, say 38 liters. Divide 38 by 4.2 to get a fuel consumption of about 9 liters per 100 km. Our fleet manages vehicles this way, with an error margin of less than 0.3 liters. The key is to refuel on level ground, as slopes can affect the actual fuel tank capacity.

[McGabriela]

Nowadays, you don't even need to calculate it yourself - the car's computer comes with this feature. In my old car, I just hold the steering wheel button to switch to the TRIP B page, and it directly shows 8.7L/100km. Newer cars are even smarter - the central display can record fuel consumption by road sections and even compare consumption between different driving modes. However, computer data might have slight deviations, so I recommend manually verifying it monthly: fill up the tank and note the mileage, then at next refill divide fuel added by distance traveled.

[AlexLee]

Don't trust the displayed fuel consumption! I've learned my lesson. The most reliable method is to measure it three times consecutively: fill up the tank, drive a few hundred kilometers, and repeat the full-tank refueling process three times. Add up the total fuel consumption from the three refills, divide it by the total mileage from the three trips, and then multiply by 100. This way, you cover all road conditions like traffic jams and highways. Last week, I measured my dad's SUV this way and got 10.3L, which was 0.8L higher than the car's computer display. Note: don't force extra fuel after the pump automatically stops—overfilling the tank can damage the carbon canister.

[LeManuel]

Remember these two numbers: current fuel amount divided by distance traveled multiplied by 100. For example, just filled up with 200 yuan worth of 95 gasoline (about 22 liters), and drove 250 kilometers on that stretch, then it's 22÷2.5=8.8L/100km. I'm used to noting it down in my phone's memo, along with the road conditions at the time. Last time during heavy rain with AC on, it soared to 11L, while on sunny highways it was only 7L—huge difference. After developing the habit of recording, you'll know when it's time to clean the throttle body.