Tarmo Kärsna: what should you know when choosing fuel, in addition to the posted price?
15. October 2026
When we look at fuel stations, we usually check the price sign first. How much does gasoline cost today, and is it a few cents cheaper at the nearby station? A few cents difference in the price per liter may seem like a clear win, but based solely on price, an important difference in the composition and energy content of the fuels may go unnoticed.
The price sign does not indicate how much energy you are buying. It is worth noting that the gasoline sold at Estonian stations is not the same. One significant difference between gasolines is the ethanol content. How can you tell which gasoline contains ethanol and which does not? The pumps are labeled with the fuel name as well as the labels E0, which means fossil gasoline, and E10 and E5, which contain 10% or 5% ethanol, respectively. The energy content of gasoline is approximately 32 MJ per liter, while ethanol has about 21 MJ per liter. Therefore, ethanol contains about one-third less energy per liter than gasoline.
If gasoline contains 10% ethanol, its energy content per liter is approximately 3% lower than that of ethanol-free gasoline. At a price of two euros per liter, a 3% difference in energy content corresponds to about six cents per liter (2 € × 3% = 0.06 €). In other words, the seemingly cheaper E10 gasoline may actually contain less energy compared to the more expensive option, contrary to initial impressions.
The actual fuel consumption and driving range depend on the car, driving style, weather, and driving conditions. However, there is a noticeable difference in energy content when the driving style is consistent and the same route is taken continuously.
The gasolines sold at Alexela are ethanol-free. This means that each liter filled contains more energy than the same type of gasoline that contains ethanol.
If the vehicle is left standing for the winter, the fuel composition also matters.
Ethanol has another property: it binds moisture from the air well. For a daily-use car, where the fuel in the tank is constantly changing, this may not have significant practical effects. A different situation arises when the same fuel remains in the tank for an extended period, as moisture and water can damage the engine's fuel systems.
In the cold season, this applies to hobby cars, motorcycles, boats, lawnmowers, and other seasonal equipment that is left standing for the winter. In such cases, it is also worth paying attention to the composition of the fuel that will remain in the tank for several months.
Therefore, when choosing fuel, it is advisable to look at what you are actually getting for your money in addition to the price sign. A cheaper price per liter does not always mean cheaper driving – a liter is always a liter, but the energy contained in it may not be the same.
