F1 | Fuel energy content to play a key role in 2026 power units
Each engine manufacturer will have to have its fuel characterized by a third-party organization, and based on the calorific value per unit mass, a different value will be assigned to each supplier, ensuring all are on an equal footing. But will this really be effective given the experimentation with new molecules?
Get ready for a 2026 season full of heated debates over the new power units. So far, we have only heard the Mercedes and Audi engines at the dyno during their fire-ups, as the power units remain largely silent. Yet, discussions over the rules governing the regulatory revolution are already intensifying. With nimbler cars, nothing will be as before, and we should expect disputes over which teams may have interpreted the grey areas creatively to extract performance.
Early controversy: Mercedes and Red Bull
The first controversy has already emerged: Mercedes (and Red Bull Powertrains) have reportedly been accused of finding a way to increase the compression ratio beyond the 16.0 limit set by the new regulations (previously, the allowable ratio was 18.0).
What is compression ratio?
Let’s briefly explain the compression ratio: it is a key parameter of internal combustion engines that indicates how many times the cylinder volume is compressed from its lowest point (BDC, Bottom Dead Center) to its highest point (TDC, Top Dead Center) before ignition occurs.
It is calculated by dividing the total volume (effective displacement + combustion chamber volume) by the combustion chamber volume. The higher the ratio, the more efficient the engine, though this also increases the risk of dangerous pre-ignition. We are talking about detonation, which can seriously impact reliability.
Thermal expansion and FIA rules
According to some rivals, Mercedes and Red Bull may have increased the hot compression ratio up to 18.0 thanks to material expansion, while the FIA immediately clarified that “… the regulations define the measurement method based on static conditions at ambient temperature. It is true that thermal expansion can affect dimensions, but the current rules do not allow measurements at elevated temperatures.”
In other words, the FIA is facing a situation similar to the flexible wings controversy in 2025, when cars passed static inspections but deformed under load. In engines, geometric changes can only occur at operating temperature. This particular case will likely be resolved, but it highlights a more sensitive underlying issue.
Energy flow measurement replaces fuel flow
From 2026, the FIA has changed the way fuel consumption is measured. Until now, a flowmeter ensured that fuel flow never exceeded 100 kg/h, but going forward, energy flow will be considered instead.
“There is a sensor that measures energy flow,” explained Enrico Gualtieri, Ferrari’s technical director for engines. “Before going on track, each manufacturer must have their fuel characterized by a third party, which will declare the energy content per unit mass of the fuel and assign a value, which will differ for each supplier.”
In other words, the available energy will be equal for all, but “… if you can produce fuel that is more energy-dense, you can put a more competitive product in the car with less weight.”
The rise of e-fuels and new experimentation
This clearly demonstrates the growing importance of environmentally-friendly fuels. E-fuels are opening a new frontier: chemical fuels without fossil derivatives could re-evaluate the role of internal combustion engines in automotive, while leaving ample room for experimentation.
The F1 regulations have left the door open for fuel research: with petroleum-derived fuels, anti-detonant additives were well-known, but chemists may discover new molecules to preserve reliability and potentially boost performance. Even an unintended underestimation in fuel calibration could lead to significant performance differences. On this topic, we are just at the beginning of a new story…
The 2026 Formula 1 season is therefore introducing a paradigm shift in how engine performance is regulated, moving from a simple 100 kg/h fuel mass limit to a complex “energy flow” measurement. As Enrico Gualtieri explains, this creates a high-stakes competition between fuel suppliers to maximize energy density and develop sophisticated e-fuel molecules. With new sensors and third-party calibrations entering the mix, the battle for 2026 supremacy will be fought in the laboratory just as much as on the track, as teams look to exploit thermal expansion and chemical innovation to gain a decisive advantage.
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