Fuel vs Energy: The Shift in IMSA Racing Terminology Explained

In the 2025 IMSA Rolex 24 At Daytona, announcers used energy instead of fuel to describe car performance. This change is due to the use of torque sensors, which measure a car’s total energy expenditure in megajoules, reflecting the hybrid and electric propulsion systems used in some cars.

The world of motorsports has seen a significant shift in terminology with the 2025 IMSA Rolex 24 At Daytona. Instead of using the traditional term “fuel,” announcers have started referring to the energy used by the cars. This change is not just a matter of semantics; it reflects a more accurate and specialized way of describing the refueling process.
The key to this change lies in the use of torque sensors. These sensors, which cost around \$60,000 to integrate into a GTD car, measure the rotational force of a drive axle. Essentially, they act as tiny onboard dynamos, providing real-time data on the car’s energy expenditure. This data is then used to regulate the ultimate range of the cars, with each car’s spec line now listing its maximum stint energy in megajoules.
For hybrid GTP cars, which have an additional 240 horsepower of electric propulsion via a spec hybrid drive system, the energy measurement is even more complex. These cars take on both liquid fuel and electrical energy during their stops. The energy recovered during a stint can be stored and reused, extending the car’s stint duration—a crucial strategy in IMSA’s endurance format.
While GTD and LMP2 cars still use liquid fuel, the use of “energy” is more appropriate for hybrid cars. The stewards at IMSA focus on the total power output rather than the specific type of fuel used. This shift in terminology is not about greenwashing but about using a more specialized and accurate descriptor that reflects the actual metric being regulated.

Why are torque sensors used in IMSA racing?
Torque sensors measure the rotational force of a drive axle, providing real-time data on a car’s energy expenditure, which is crucial for regulating the ultimate range of the cars.
How do hybrid GTP cars differ from other cars in terms of energy measurement?
Hybrid GTP cars take on both liquid fuel and electrical energy during their stops, with the energy recovered during a stint being stored and reused to extend the car’s stint duration.
What is the significance of using “energy” instead of “fuel” in IMSA racing?
The use of “energy” is more accurate because it reflects the total power output, including both liquid fuel and electrical energy, which is what the stewards at IMSA are regulating.
How do torque sensors impact the refueling process in IMSA racing?
Torque sensors provide real-time data on a car’s energy expenditure, allowing for more precise regulation of the refueling process and ensuring that each car’s maximum stint energy is accurately measured.
What are the implications of this shift in terminology for the sport?
The shift to using “energy” instead of “fuel” reflects a more specialized and accurate way of describing the refueling process, which aligns with the complex energy dynamics of hybrid and electric propulsion systems used in some cars.

The shift from fuel to energy in IMSA racing terminology is a reflection of the evolving technology and complex energy dynamics in modern motorsports. The use of torque sensors and the integration of hybrid and electric propulsion systems necessitate a more accurate and specialized descriptor, making energy the more appropriate term for describing the refueling process in these high-performance vehicles.