# How to calculate fuel consumption and reduce car fuel consumption?

Oil prices are constantly rising, and drivers are becoming more and more worried about fuel consumption of their cars. Although exact fuel consumption of a car always varies depending on situation, factors such as city roads or highways, road conditions, tire pressure and other factors will affect fuel consumption, but it is not difficult to calculate the fuel consumption of a car.

Method 1

Calculation of one-time fuel consumption

1 First, formula for calculating fuel consumption is "mileage divided by amount of fuel used". The fuel consumption of a car is number of kilometers it can travel on one liter of gasoline. If you know how far your car has traveled and how many liters are in tank, you can simply divide mileage by volume to get "kilometers per liter" or kilometers per liter (km/l).

• The same can be done with gallons and miles.
• The best time was recorded immediately after refueling car.
• 2 After refueling, reset "mileage" to zero. New cars have trip meters that can be reset at any time. The odometer is usually located on dashboard or center console and can be reset by pressing and holding a small button. Reset odometer to zero when refueling and check it at next refueling. This is number of miles you have driven since you last refueled.

• Your odometer will show "0".
• If vehicle does not have an odometer, distance traveled can be recorded as "starting distance". For example, if car has traveled 10,000 kilometers on a full tank, write "10,000".
• 3 Record mileage on odometer before next gas station. Record mileage on odometer as "final mileage" before refueling at gas station.

• If your car doesn't have an odometer, subtract "Mileage From" from current mileage to get trip distance. For example, if the mileage is displayed as 10,250, then subtract 10,000, which means that you have traveled 250 kilometers on this tank of gasoline.

4 drove car until it almost ran out of gas. You can do this no matter how much fuel is left in tank, but more fuel you use, more accurate reading will be.

5 Record amount of fuel. Fill tank completely, noting how much fuel is required to fill it. This is your "gas usage".

For this calculation, tank must be fully filled, otherwise it is not known how much gasoline has been used since last refueling.

6. Divide mileage by amount of fuel to calculate vehicle's fuel consumption. The results show how many miles you drive per liter of gasoline. For example, if you drive 540 km to a gas station and fill tank with 45 liters of gasoline, fuel consumption will be 12 km per liter or 12 km/liter (540 km/45 l = 12 km/l).

• If you calculate in kilometers and liters, you must divide fuel used by kilometers traveled per 100 to get "fuel consumption per 100 kilometers".
• You must start with a full tank and end with a full tank to know exactly how much gas vehicle is using.
• 7 Let's practice calculation with an example. Terry's odometer showed 37,835 kilometers when he filled up. After several days of driving, he needed to refuel when 38,460 km was on odometer, and 45 liters were required to refuel. What is his fuel consumption?

• Fuel consumption = (final mileage - initial mileage) / gasoline consumption.
• Fuel consumption = (38460km - 37835km) / 45 liters
• Fuel consumption = 625 km/45 liters
• Fuel consumption = 14 km/l
• Method 2

Calculate average fuel consumption

1 Please note that fuel consumption varies with driving conditions. For example, stopping and starting a car uses much more gasoline than driving at a constant speed. Therefore, fuel consumption at high speeds is always lower than on city roads.

• Cruise control helps reduce fuel consumption.
• The faster you drive, worse fuel consumption.
• Because car air conditioner requires gasoline to cool, turning on air conditioner will increase fuel consumption.
• 2 Continuously record fuel consumption of several full tanks to get an average fuel consumption. More data is needed to get a better picture of a car's fuel consumption. Calculating average fuel consumption over longer driving periods eliminates "glitches" in data.

• For example, when you are driving in mountains, you calculate your daily gas mileage. Since it takes more fuel to climb a mountain, your fuel consumption will seem much higher than normal.
• 3 After refueling, reset odometer. Reset odometer to zero and do not reset until next gas station. If your car does not have an odometer, write down mileage on car after refueling.

4Keep a record of amount charged each time you fill up. For a more accurate measurement of fuel consumption, it is necessary to know amount of fuel used. Every time you refuel, record amount of refueling and keep it well.

5. Drive your car as usual for a few weeks. Do not reset odometer while driving. Add oil 3-4 times to get accurate readings. Try to drive this route evenly throughout month, as long trips or unexpected traffic jams can change fuel consumption.

• There is no need to add gasoline every time. If amount of fuel filled is recorded each time, fuel consumption can be calculated.
• 6 Refuel gas tank every 2-3 weeks. To calculate fuel consumption, fill fuel tank and record fuel consumption.

7. Add up all dressing quantities. This gives total amount of fuel used during this time.

• If I fill up three times, 45 liters, 10 liters and 40 liters, my total fuel capacity is 95 liters.
• 8 Divide total mileage by total fuel consumption. Use odometer to see how many miles you have driven, then divide it by your total fuel consumption to calculate your average fuel consumption. Although this is only an accurate fuel consumption during test period, it is a good estimate of vehicle's average fuel consumption.

• For example, if you filled in 95 liters of gasoline and drove 820 km in that time, your average fuel consumption would be 8.7 km per liter (820 km/95 liters = 8.6 km/liter).
• 9 You should be aware that car advertisements often inflate fuel consumption. Automakers are required by law to publish data on average gas mileage of their vehicles. But these are estimates, and often overestimated. You can check your car's fuel consumption online through US Department of Energy website, but you'll have to do your own calculations to figure out your car's actual fuel consumption.

• If your calculations differ significantly from suggested averages, you may need to take car to a mechanic for inspection.
• Method 3

Reduce fuel consumption

1 Avoid using air conditioners. The air conditioner uses gasoline to cool car, which means less gasoline is actually used to drive car. Increasing temperature of air conditioner or turning it off after vehicle has cooled down can improve efficiency of vehicle.

• Turning on air conditioner at maximum power can reduce fuel consumption by almost 25%.
• 2. Drive within set speed. The faster you drive, more fuel you use. This is not a small number. When speed of car exceeds 80 kilometers, each increase of 8 kilometers per hour is equivalent to paying a few dollars more per liter of gasoline.

3 Safe driving. It takes more energy to start a car than it does to keep it going. This means that if you constantly follow car in front of you too closely, always stop and restart or overtake, you will consume much more gasoline than if you were driving at a constant speed.

• Try not to brake or accelerate sharply. Brake early and do not press on brake pedal.
• 4 On long, flat roads, try using cruise control. Cruise control maintains a constant and even vehicle speed, avoiding sporadic accelerations and preventing unnecessary fuel from being burned.

5 Stop engine in traffic jams. Idling or driving in a parking lot wastes gas and isn't going anywhere. If possible, turn off engine to save precious gasoline.

6. Avoid containers on roof. This can significantly reduce aerodynamic performance of car, slow it down and increase fuel consumption. Generally speaking, towing a trailer or trunk is more economical option.

7 Maintain tire pressure. Fuel consumption can increase by 0.3% if all four tires are under-inflated. Most air pumps at gas stations are free to use and will inflate your tires to pressure recommended in your vehicle's owner's manual.

• Some vehicles have stickers on driver's side door or in glove compartment indicating correct tire pressure.
• 8 Replace air filter. This is one of cheapest and easiest ways to improve your fuel efficiency. Tell your local auto shop make, model, and year of your vehicle and ask dealer for advice on choosing right air filter for your vehicle. Every car needs its own air filter.

• For newer vehicles, replacing air filter may not improve fuel efficiency, but will allow vehicle to accelerate more easily without problems.
• Tips

• Replace engine air filter.
• Don't waste fuel on erratic acceleration and deceleration, especially in large SUVs or sedans.
• Maintain tire pressure as recommended by manufacturer.
• Do not use car air conditioner.
• Watch speed limit signs on road.
• Warning

• Use a calculator to avoid arithmetic errors.