Blog about life, money and time

Blog about life, money and time

Real fuel usage of your car
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How high is real fuel usage of your car (calculator)

Actually, this article should be part of the household budget cycle – the first entry in this topic is here. But to the point. Most of us own a vehicle, that we use, or maybe plan to buy, a car. The main cost factor is, of course: the fuel. Fuel consumption in a car is probably the main factor, that every potential user pays attention, when buying a car or other vehicle. What is real fuel usage of your car?

Declared fuel usage

I know from my own experience (I am the proud owner of a car ?) and it is probably not surprising, that the fuel usage figures declared by car producers are often inconsistent with the real results. Fuel consumption measured in laboratories at the factories is not equal to the daily fuel consumption per 100 km we experience.

Why is it happening. These tests are carried out under optimal, standardized test conditions, where especially: the speed of the tested vehicle does not exceed the optimal value. Second – the air conditioning turned off, the start & stop system works without any disturbances. Additionally, the temperature around is so high, that there is no need to warm up the engine. The tires used, have low rolling resistance. Aside from the fact, that the driving style of the test driver is probably different to the typical driving in a crowded city. The standardization of this measurement is aimed at the comparability of combustion between individual models. It does not change the fact, that the information is not always useful for the users, because in fact the cars consumes in general much more fuel than is declared by the manufacturer.

To start lowering your fuel consumption costs, you must first:

  1. Find out what influences at the amount of fuel usage.
  2. Calculate for yourself how much fuel your car actually use.

What factors affect car fuel consumption

So what influences fuel consumption in a car? A number of variables are like that:

  1. weather conditions. Using the car in winter causes the engine to be started many times at low or very low temperatures.
  2. Air conditioning on – especially in summer.
  3. The amount of luggage carried, as well, as the number of passengers carried. It often increases the weight of the entire vehicle by only a few percent, which, however, affects fuel usage.
  4. Driving style. Driving in a city, especially when it is crowded, forces frequent braking and acceleration. Moving off with the proverbial “heavy leg” can cause temporary burning up to 5 times greater than during normal driving. When driving on the highway at higher speeds, by contrast, air pressure is the biggest contributor to fuel consumption, which increases significantly at higher speeds. Detailed rules for economical driving can be found on a number of pages.
  5. Remember about the quality of the tires. Winter tires in summer don’t help.

My car board computer

Reading the fuel usage from my on-board computer, I can see that the readings are inconsistent with reality. From the manual, I learned, that the computer takes into account the previously traveled route. For example, if you are driving around the city and then going on a highway trip, the figures of fuel usage are statistically calculated on the basis of the previous route – these numbers can really surprise you.

How do we calculate the actual fuel usage of a car

In the attachment below there is a simple Excel calculator, with which you can record the real fuel usage of car. You only enter only data when refueling, the number of liters of fuel refueled and the price of 1 liter. As a result you will get:

  1. fuel consumption per 100 km,
  2. cost of driving during 100km.


In the attachment there is an example of how to fill in the file. Note: in order for the calculator to give correct results, you must refuel your car to full level your fuel tank – each time.

I will be happy, if this post is useful for you and let you save some money. I have a request to like my Facebook page and coments .

Below there are some my other posts, that I invite you to read:

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