Horse Powertrain and Repsol have unveiled a next-generation hybrid powertrain that achieves ultra-high efficiency and low fuel consumption, operating on 100% renewable gasoline.
The Horse H12 Concept engine features combustion system improvements and delivers reduced internal losses. It achieves a peak brake thermal efficiency of 44.2% and reduces vehicle fuel consumption to below 3.3l per 100km under WLTP testing — approximately 40% lower than the 2023 average for new passenger car registrations in Europe.
Maximizing efficiency reduces fuel consumption and CO₂ emissions proportionally. Using 100% renewable fuel, a mid-size car with the Horse H12 Concept powertrain driving 12,500 km per year is estimated to emit 1.77 tons less CO₂ annually than a conventional fuel-powered car.
The hybrid powertrain system’s H12 Concept is an evolution of the HR12 engine and includes an innovative combustion system designed at a 17:1 compression ratio, a latest-generation exhaust gas recirculation system (EGR), an optimized turbocharger, a high-energy ignition system and an improved hybrid gearbox with optimized energy management, and reduced internal friction enabled by new Repsol lubricants.
The project, led by teams from the Horse Technologies Division in Valladolid and the Repsol Technology Lab in Madrid, has produced its first two prototypes and validated performance. The first demonstrator vehicle is expected to be presented in early 2026. This is the first step toward industrial production of highly-efficient hybrid engines.
More than 97% of Europe’s current vehicle parc (ACEA) is still combustion-based, so delivering solutions capable of reducing CO2 emissions today – such as highly efficient engines and alternative fuels – play a complementary role alongside electrification, hydrogen, and other emerging technologies on the road to mobility net zero.
Scaling these solutions requires that the current CO₂ standards for light-duty vehicles provide a clear, long-term framework. This framework should acknowledge the role of highly efficient engines using renewable fuels in decarbonizing road transportation and maintain a technology-neutral approach beyond 2035 to support innovation and industrial investment.
Luis Cabra, executive managing director of energy transition, technology, institutional affairs and deputy CEO of Repsol, stated, “This collaboration shows that decarbonization can be accelerated through innovative and accessible technological solutions. The use of 100% renewable fuels is a net zero emission solution, complementary to electric vehicles, for decarbonizing the transport sector. Supporting clear and ambitious regulation that drives investment in renewable fuels and highly efficient engines is essential for Europe to reduce transport emissions faster in a more competitive and effective manner.”
Patrice Haettel, chief operating officer at Horse Powertrain and chief executive officer at Horse Technologies, added, “The Horse H12 Concept is an example of how highly efficient engines and renewable fuels can reduce emissions today, without waiting for future solutions. As a company, we believe that relying on a single technology is not the fastest way to cut emissions. This is why we advocate a technology neutral approach that enables innovation across all solutions – electric, hybrid, range extenders and low-carbon fuels.”
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