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How do you calculate the average fuel consumption of a car?

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For those interested in buying a specific car model, one of the most important parameters is average fuel consumption. How to calculate a car’s fuel consumption? Learn the formula and check whether you can reduce your consumption of gasoline, diesel fuel, or natural gas.

Before buying a car, many drivers pay attention to consumption rates for a given model of car, among other things. The larger the consumption, the more one will have to spend on fuel. Would you like to check how much fuel per 100 kilometers of driving the car you already have or are interested in buying consumes? You can do it in a number of ways.

What is fuel consumption?

Fuel consumption is one of the most significant factors affecting the costs of operating a car in a given time. It is presented in liters per 100 kilometers driven in a car. Therefore, if you know the price of gasoline, diesel fuel, or natural gas, you can calculate how much you will pay on average for driving a given distance.

However, fuel consumption is different when driving in city traffic and different on long trips, so the value is averaged. Still, such data is very useful when buying a car. Average fuel consumption allows for calculating the costs of operating a car (e.g., in a monthly or yearly perspective) and then comparing it with a different model. It is worth knowing that differences between some cars can range from a few hundred to a few thousand zloty a year.

Does the data provided by the car manufacturer suffice to calculate fuel consumption?

Car manufacturers publish information on fuel consumption on their websites. This way, you do not need to calculate the consumption level on your own. However, in most cases, it only applies to new models. A problem may arise when you are interested in an older car: then, it may be necessary to contact a representative of the car manufacturer.

Furthermore, fuel consumption data is provided based on tests which are usually carried out under very specific conditions before the car is put on sale. As a result, their basic goal is to study the number of harmful substances emitted to the environment rather than estimate the costs of operation.

How the manufacturer’s data can differ from real fuel consumption? For instance, on its website, Volkswagen claims that the Tiguan with a diesel engine consumes from 5.1 to 10.1 l per 100 km. And there is nothing strange about this, since, as we have mentioned, a car may consume less fuel in city traffic and more fuel on long routes. And so, it is a good idea not only to accept the information provided by the manufacturer but also to calculate the costs of operating the car in relation to your individual driving style and pattern.

How to make use of fuel consumption reports?

Fuel consumption is a popular topic; therefore, the industry quite often updates reports to include new models available in the offers of car manufacturers. Such rankings constitute yet another source that allows finding information on the fuel consumption of a given car without a need to calculate it on your own. Below, we present examples of data from autocentrum.pl.

Fuel consumption in different car models

Car model and fuel typeAverage consumption per 100 kmAverage consumption manufacturer’s declaration
Dacia Duster II 1.0 TCe LPG 100KM 74kW – natural gas8.1 lno data
Citroen C5 Aircross SUV 1.6 PureTech 181KM 133kW – petrol7.8 l5.7 l
Fiat Tipo I 1.7 D 58KM 43kW – diesel5.7 l6.1 l
Ford Escape I 2.0 i 16V XLS 129KM 95kW – petrol6.8 l9.7 l
Hyundai IX20 Mikrovan 1.4 CRDI 77KM 57KW – diesel5.6 l4.5 l
Mazda 2 III Hatchback 5D 1.5 SKY-G 75KM 55kW – petrol5.6 l4.7 l
Kia Soul II 1.6 VGT CRDi 128KM 94kW – diesel6.0 l5.5 l
Nissan 370Z Roadster 3.7 V6 328KM 241kW – petrol12.9 l11 l
Opel Astra J Sports Tourer 1.3 CDTI ecoFLEX 95KM 70kW – diesel5.7 l4.1 l
Skoda Octavia II Kombi 1.6 i 16V FSI 115KM 85kW – petrol7.7 l6.6 l
* Based on “Fuel consumption” reports from www.autocentrum.pl

How does the onboard computer calculate consumption?

Currently, most new cars are fitted with an onboard computer, which, among others, calculates the average fuel consumption in real-time and provides this information to the driver. It needs to be remembered that the result of the reading will change depending on driving conditions. Therefore, more reliable information on average consumption may be obtained after completing a route than during driving. This way, it is easier to calculate the real costs of operating the car.

How to calculate your car’s fuel consumption on your own?

Would you like to calculate your car’s fuel consumption easily? It will require only a few steps:

  • fill up the fuel tank to the brim;
  • after filling up, note down the odometer reading or reset the trip meter (if available);
  • drive a specific distance (e.g., 25 km);
  • fill up the fuel tank to the brim again.

Now, take the amount of fuel poured into the tank in the last step, divide it by the number of kilometers driven, and multiply the result by 100. The result will be fuel consumption in liters per 100 km.

The formula for calculating fuel consumption is very simple:

Average consumption = (fuel used/ number of kilometres) x 100

What affects average fuel consumption?

Drivers whose cars consume a lot of fuel often wonder what factors affect their fuel consumption and how to reduce it. It turns out that there are many factors that impact fuel efficiency. They include:

  • Engine capacity and power. The correlation between engine parameters and fuel consumption is straightforward: the bigger the capacity, the more fuel we’ll need.
  • Tyre pressure. The lower the tyre pressure, the higher the rolling resistance, which results in higher fuel consumption.
  • Gear shifting. Changing gears when the revs are too low or too high (uneconomic driving) also has a negative effect on fuel efficiency.
  • Air-conditioning. Car owners appreciate AC, especially in the summer months; however, since activated AC drains energy from the drive train and the electric system, it also increases fuel consumption.
  • Bad technical condition of the car. High fuel consumption may be caused by worn-out spark plugs, dirty filters, or a broken thermostat. Therefore, it is worth keeping the car well maintained and replacing worn-out elements.
  • Open windows during driving. It increases air resistance, which reduces the car’s aerodynamics, resulting in increased fuel consumption.

Overloading the vehicle. It is worth having a look at all the stuff that you have been carrying in the boot for ages. Its weight does affect average fuel consumption. Also important is the number of passengers driven in a car.

It can be assumed that each additional 100 kg of carload increases fuel consumption by 0.6 liters of fuel per 100 km (with a vehicle weighing 1,500 kg net). The additional fuel consumption caused by passengers can be calculated using the following formula:

Additional consumption = (average weight of one person in kg * number of passengers * 0.6) / 100

source: kalkulator-paliwa.pl

In order to find the value of additional costs of regularly carrying a few passengers in a car, we have compared average consumption and driving costs for selected car models before and after, including the number and weight of passengers.

We assumed that the same car is used to carry 4 people to work every day (the average weight of one passenger being 70 kg). Each month, they cover a distance of 800 km (20 work days by 40 km).

Additional costs of fuel consumption when carrying 4 people

Car modelFuel typeFuel price* (PLN)Average consumption (per 100 km)Monthly fuel consumption/ cost of trip without passengersMonthly fuel consumption/ cost of trip after including the number and weight of passengers
Dacia Duster II 1.0 TCe LPG 100KM 74kWnatural gas3.378.1 l64.8 l / PLN 218.3778.24 l / PLN 263.66
Citroen C5 Aircross SUV 1.6 PureTech 181KM 133kWpetrol 988.037.8 l62.40 l / PLN 501.7275.84 l / PLN 608.99
Fiat Tipo I 1.7 D 58KM 43kWdiesel7.505.7 l45.60 l / PLN 34259.04 l / PLN 442.80
Ford Escape I 2.0 i 16V XLS 129KM 95kWpetrol 957.376.8 l54.40 l / PLN 400.9267.84 l / PLN 499.98
Nissan 370Z Roadster 3.7 V6 328KM 241kWpetrol 988.0312.9 l103.20 l / PLN 828.69116.64 l / PLN 936.61
Kia Soul II 1.6 VGT CRDi 128KM 94kWdiesel7.506.0 l48.0 l / PLN 36061.44 l / PLN 460.80
Volkswagen Passat 1.6 102 KM 75 kWnatural gas3.378.3 l66.40 l / PLN 223.7679.84 l / PLN 269.06
* Source: autocentrum.pl: average fuel prices as at 8 July 2022; calculation results: kalkulator-paliwa.pl

The costs of covering a given trip also depend on the type of fuel used in the car. The examples above show that cars fuelled by natural gas will generate the least costs (in the calculation, we omitted the costs of filling up with petrol necessary to, e.g., start the engine). However, it is worth noting that it is not the only expense connected with maintaining a car.

As a rule, owners of cars with natural gas installations face higher costs of repairs, inspections, legalization of tanks, or insurance compared to traditional petrol cars. Often, the owner also needs to cover the costs of installing the natural gas installation (up to a few thousand zloty).

How to reduce fuel consumption through eco-driving?

If you are wondering how to reduce fuel consumption, it is a good idea to start by changing your habits. Your driving style has a significant impact on how much you spend on fuel per year. The good news is that one can learn to drive economically: it is only a matter of adopting new habits.

Basic rules of eco-driving:

  • pull off right after starting the engine;
  • turn the engine off during stops;
  • apply engine braking;
  • control tyre pressure;
  • avoid driving in low revs;
  • do not overload the car;
  • turn AC off whenever possible.

By applying the above recommendations, a driver is able to save about 20-25% of fuel compared to traditional driving.

Worth knowing: How to calculate fuel consumption

  • Information on the fuel consumption of a given car model can be obtained from the manufacturer or automotive reports, or it can be calculated on one’s own.
  • The formula for calculating average fuel consumption is simple: average consumption = (fuel used / number of kilometres) x 100.
  • A car’s fuel consumption is affected by multiple factors, e.g., engine capacity and power, gear shifting style, or speed.
  • The driving style has a large impact on fuel economy. By eliminating negative habits, one can reduce their car’s fuel consumption.

How does the fuel type affect third-party liability insurance?

The type of fuel is one of the factors affecting the prices of third-party liability insurance. The cheapest insurance policies are usually available to owners of electric cars. Such cars are, as a rule, much newer compared to traditional cars. Therefore, insurance companies perceive electric cars as safer than cars with internal combustion engines, which results in a lower insurance premium. However, it is always a good idea to compare car insurance prices using a comparison service, as it can save you some money.

Source: insurance comparison site rankomat


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