Calculating Fuel Consumption: A Comprehensive Guide
Although the exact fuel consumption of a vehicle always changes with the situation, whether it is a city road or a highway, road conditions, tire pressure, and other factors will affect fuel consumption, it is not complicated to calculate the fuel consumption of a vehicle.
Calculate Single Fuel Consumption
First of all, the formula for calculating fuel consumption is “mileage divided by the amount of fuel used.” A car’s fuel consumption is the number of kilometers it can travel per liter of gasoline. If you know how far your car has been driven and how many liters of fuel is in the tank, you can simply divide the mileage by the amount of fuel to get “kilometers per liter” or kilometers per liter (km/l).
- The same calculation can be done in gallons and miles.
- The best time to record is after the car is refueled.
After filling up the tank, reset the “trip odometer” to zero. Newer cars have trip odometers that can be reset to zero at any time. The trip odometer is usually on the dashboard or center console and can be reset to zero by pressing and holding a small button. Set the trip odometer to zero when you fill up, and check it the next time you need to refuel. This is the mileage since your last refueling.
- Your trip odometer will show “0”.
- If there is no trip odometer on the car, the mileage can be recorded as “starting mileage”. For example, if the car has 10,000 kilometers on the tank, write “10,000.”
Before your next refueling, record the mileage on the odometer. Before filling up at a gas station, record the mileage on the odometer as “final mileage.”
- If your car doesn’t have a trip odometer, subtract the “starting mileage” from the current mileage to find the trip distance. For example, if the mileage is shown as 10,250, then subtract 10,000, which means you drove 250 kilometers on this tank of fuel.
Drive until you are almost out of gas. This calculation works regardless of how much oil is left in the tank, but the more oil used, the more accurate the reading will be.
Note the amount of oil. Fill the tank, noting how much fuel is needed to fill the tank. This is your “gas usage”.
- You have to completely refill the tank for this calculation, otherwise, you won’t know how much gas has been used since the last time you filled it up.
Calculate the car’s fuel consumption by dividing the mileage by the amount of fuel. The results show the mileage per liter of gasoline. For example, if you drive 540 kilometers before refueling and fill the tank with 45 liters of gasoline, your fuel consumption is 12 kilometers per liter, or 12 kilometers per liter (540 kilometers / 45 liters = 12 kilometers per liter).
- If calculated in kilometers and liters, the amount of fuel used in driving kilometers should be divided by 100 to get the “fuel consumption per 100 kilometers.”
- You have to start with a full tank of gas and end with a full tank of gas to know exactly how much gas the car consumes.
Let’s practice calculations with an example. Terry’s odometer read 37,835 kilometers with a full tank of gas. After driving for a few days, he needed to refuel. At this time, the odometer read 38,460 kilometers, and it took 45 liters to refill the tank. What’s his fuel consumption?
- Fuel consumption = (final mileage – starting mileage) / gasoline consumption
- Fuel consumption = (38460 kilometers – 37835 kilometers) / 45 liters
- Fuel consumption = 625 kilometers / 45 liters
- Fuel consumption = 14 kilometers/liter
Calculate Average Fuel Consumption
Keep in mind that fuel consumption will vary based on driving conditions. For example, stopping and starting a car consumes much more fuel than driving at a constant speed. This is why fuel consumption on highways is always lower than consumption on city roads.
- Cruise control can help you get better gas mileage.
- The faster the speed, the worse the fuel consumption.
- Since the car air conditioner requires gasoline for cooling, turning on the air conditioner will increase fuel consumption.
Continuously record the fuel consumption of several full tanks to get the average fuel consumption. To get a more accurate picture of a car’s fuel consumption, more data is needed. Calculating average fuel consumption over longer driving periods removes “glitches” in the data.
- For example, when you drive into the mountains, you calculate your fuel consumption for the day. Because climbing hills require more fuel, your gas mileage will appear to be much higher than usual.
After filling up the tank, reset the trip odometer to zero. Return the trip odometer to zero and do not reset it until your next refueling. If your car doesn’t have a trip odometer, write down the mileage on your car after filling up.
Record the amount of refueling each time you refuel. In order to measure fuel consumption more accurately, you need to know the amount of oil used. Every time you refuel, write down the amount of oil and keep it.
Driving normally for a few weeks. Do not reset the trip odometer while driving. Refuel 3-4 times to get an accurate reading. Try to drive this evenly throughout the month, as long journeys or unexpected traffic jams can change fuel consumption.
- No need to top up the oil every time. As long as the amount of fuel refueled is recorded each time, the fuel consumption can be calculated.
Fill the tank every 2-3 weeks. To calculate fuel consumption, fill up the tank and note the amount.
Add up all oil volumes. This gives the total amount of oil used during this period.
- If I refuel three times, 45 liters, 10 liters, and 40 liters, then my total refueling volume is 95 liters.
Divide total mileage by total fuel volume. Use the trip odometer to check the number of miles driven, then divide by the total fuel consumption to calculate the average fuel consumption. While this is only the exact fuel consumption during the test, it’s a good estimate of the car’s average fuel consumption.
- For example, if you fill up with 95 liters of gasoline and drive 820 kilometers during this period, the average fuel consumption is 8.7 kilometers per liter (820 kilometers / 95 liters = 8.6 kilometers/liter).
You know, fuel consumption is often overestimated in car ads. By law, car manufacturers are required to publish the average fuel consumption of their cars. But this is only an estimate, and often an overestimate. You can check your car’s fuel consumption online through the U.S. Department of Energy’s website, but to get your car’s actual fuel consumption, you’ll have to do the calculations yourself.
- If your calculations differ significantly from the recommended average, you may need to take your car to a technician for inspection.
Reduce Fuel Consumption
Avoid using air conditioning. The air conditioner uses gasoline to cool the car, which means less gasoline is actually used to drive. Turning up the air conditioning temperature or turning it off after the car has cooled down can improve your car’s efficiency.
- Turning the air conditioning to maximum can reduce fuel economy by nearly 25%.
Drive within the speed limit. The faster you drive, the more fuel you use. This is not a small number. When the vehicle speed is above 80 kilometers per hour, every 8 kilometers per hour increase in speed is equivalent to paying a few more yuan per liter of gasoline.
Defensive driving. It takes more energy to start a car than to keep it moving. This means that if you often follow the car in front too closely, always stop and start again, or overtake, you will consume far more gasoline than driving at a constant speed.
- Try not to brake or accelerate hard. Brake early and don’t slam on the brake pedal.
On long, flat stretches, use cruise control whenever possible. Cruise control keeps the car at a consistent and even speed, preventing unnecessary burning of fuel when accelerating and stopping from time to time.
Turn off in heavy traffic. Idling or driving when the car is not moving wastes gas and gets you nowhere. If possible, shut down the engine to save precious gas.
Avoid using roof boxes. This significantly reduces the car’s aerodynamics, slows it down, and uses more fuel. Generally speaking, towing a trailer or a trunk is a more fuel-efficient option.
Keep tires fully inflated. If the tire pressure in all four tires is low, fuel consumption may increase by 0.3%. Air pumps are available free of charge at most gas stations to inflate your tires to the pressure recommended in your car’s manual.
- Some cars have a sticker on the driver’s side door or glovebox listing the appropriate tire pressure.
Replace the air filter element. This is one of the cheapest and easiest ways to improve fuel efficiency. Tell your local car shop the make, model, and year of your car, and ask the store clerk for recommendations to make sure you buy the right air filter for your car. Every car requires a different air filter.
- On a new car, replacing the air filter may not help improve fuel efficiency, but it will make it easier for the car to accelerate without problems.
Tips
- Replace the engine air filter.
- Don’t waste fuel by accelerating and decelerating erratically, especially in a large SUV or sedan.
- Maintain tire pressure as recommended by the manufacturer.
- Avoid using your vehicle’s air conditioner.
- Observe the speed limit signs on the road.
- Use a calculator to avoid arithmetic errors.