It is also a lesson on applying appropriate data transformations. The above is an illustration of why when using our fuel consumption calculator, as well as other such tools, it is important to keep track of the end goal and define the question at hand precisely, before measuring and making conclusions. Note that the km/l average is not misleading here, as it is 2.5 km/l, and 2 x 2.5 = 5, which is correct. It follows that type A is more efficient than type B using this definition. If we give each car of type A a liter of fuel, they will cover 5 kilometers combined while giving each car of type B a liter of fuel, they will cover only 4 km combined. However, if you define efficiency as covering the greatest distance given a certain fuel amount, then the US researcher would be correct. Therefore, type B is more efficient than type A. For type B both researchers will correctly estimate that 100 liters will be required for the same task. The French will get it right by multiplying 200 x 0.625 = 125. Here is an explanation why: if you were to take both cars of type A and want to cover 100 kilometers with each of them, you would need not 200 / 2.5 = 80 liters, but 125 liters of petrol (100 liters for the first car and 25 liters for the second). In such a case the French researcher is correct, as the average is misleading the US researcher. Most people would argue that when we care about how much fuel we would need to cover a given distance. The issue is what we care about when we calculate fuel consumption and fuel efficiency. The two researchers would come to different conclusions as they are using different metrics!īut who is right in the above example? The fuel consumption calculation is correct in both cases. The French will see that for type A the average is 0.625 while for type B it is 0.5 and will conclude that type B is more efficient than type A, as the car will use less fuel to cover the same distance. The US engineer will see that for type A the average is 2.5 while for type B it is just 2.0, concluding that type A is more efficient than type B as it can cover a greater distance with a liter of diesel, petrol, gas, etc. You have each researcher record the efficiency of 2 cars of each type, or, alternatively, the consumption of one and the same car in two different environments (the data available is the same for both), and the results recorded by them look like so:Īverage above means the arithmetic mean. You put two researches, one American and one French, to the task, with the first using kilometers per liter as an efficiency metric, while the second using liters per km. Understanding that is key for the correct interpretation and comparison of fuel consumption estimates such as those produced by this calculator.įor example, say you want to compare two types of cars: A and B. Different ways to calculate fuel economyįuel efficiency, or fuel economy, can be a tricky concept. For example, if you notice that your usually spend $0.15 per mile (15 cents per mile), then if you know you will be travelling for 200 miles, you can calculate the cost of the trip by multiplying 200mi x $0.15 = $30 for a 200 mile trip. These are very useful when estimating your fuel costs and can help you predict your expenses easier on a future trip. The result depends on the metrics used as input: miles per gallon if the input was in miles and gallons, and km per liter if the input was in kilometers and liters.Īdditionally, the fuel consumption calculator will output the fuel cost per mile or fuel cost per km, depending on the metric units selected, as well as miles per $ / km per $. The formula for calculating fuel consumption used in this online fuel consumption calculator is:įuel consumption = Fuel used / Distance travelled Different ways to calculate fuel economy.