By ATN
Summary: Horse Powertrain and Repsol have unveiled the HORSE H12 Concept hybrid engine, a next-generation high-efficiency powertrain operating on 100% renewable gasoline. The system achieves 44.2% peak brake thermal efficiency and reduces fuel consumption by 40% compared with the 2023 European average, lowering usage to below 3.3 L/100 km under WLTP testing. In a mid-size vehicle driving 12,500 km annually, the renewable-fuel hybrid setup can cut CO₂ emissions by 1.77 tons per year versus a conventional combustion vehicle. The project highlights a technology-neutral pathway to near-term transport decarbonization while leveraging Europe’s existing combustion-heavy vehicle fleet.
Key engineering takeaway: The H12 Concept combines a 17:1 compression-ratio combustion system, advanced EGR, optimized turbocharging, high-energy ignition, reduced-friction lubricants, and an improved hybrid gearbox with energy management to reach 44.2% BTE. Rather than replacing combustion outright, the design extracts significantly higher thermodynamic efficiency while pairing with renewable fuel to maximize lifecycle CO₂ reduction.
Why it matters: With over 97% of Europe’s vehicle parc still combustion-based, scalable efficiency gains and drop-in renewable fuels offer immediate emissions reductions without waiting for full electrification turnover. The program also underscores how regulatory support for technology neutrality could unlock faster, lower-cost decarbonization across existing infrastructure and industrial capacity.
HORSE H12 Concept hybrid engine runs on 100% renewable fuel
Horse Powertrain, via its Horse Technologies division, 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 introduces enhancements to the combustion system and reductions in internal losses, achieving 44.2% peak brake thermal efficiency (BTE) while reducing vehicle fuel consumption by 40% (in comparison with 2023 average passenger car new registration in Europe)1 to below 3.3 liters per 100 kilometers, according to standardized European testing (WLTP).
Maximizing efficiency directly results in lower fuel consumption and lower CO2 emissions in equal proportions. When using the 100% renewable fuel, a mid-sized car equipped with the HORSE H12 Concept powertrain and driving an average of 12,500 kilometers per year, will emit 1.77 tons of CO₂ per year less than a vehicle with a traditional fuel and combustion engine.1, 2
The hybrid powertrain system incorporates the HORSE H12 Concept engine, an evolution of the HR12 engine that includes an innovative combustion system designed at a 17:1 compression ratio, a new-generation exhaust gas recirculation system (EGR), an optimized turbocharger, a high-energy ignition system, and an improved hybrid gearbox with optimized energy management, as well as 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 towards industrial production of highly-efficient hybrid engines.
This project contributes to the mobility sector’s transition to net zero, applying the principle of technology neutrality, and demonstrates how innovation can provide near-term CO2 reduction solutions.
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.
For these solutions to scale, it is essential that the current revision of CO₂ standards for light-duty vehicles includes a clear, long-term framework. It should recognize the role of highly efficient engines powered by renewable fuels in road-transport decarbonization, ensuring a technology-neutral approach beyond 2035 to support innovation and necessary industrial investments.
Luis Cabra, Executive Managing Director of Energy Transition, Technology, Institutional Affairs and Deputy CEO of Repsol, states: “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, adds: “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.”
In October, Repsol achieved a technological milestone by producing gasoline of 100% renewable origin at industrial scale at its Tarragona facility. This new product is compatible with existing gasoline vehicles, with no modifications required. Nexa 95, Repsol’s highest-quality 95-octane renewable gasoline, is already available at 30 service stations in Spain.
The company also offers renewable diesel at close to 1,500 service stations in Spain and Portugal, making it the largest distribution network of renewable fuels in Europe.
Repsol is the leading producer of renewable fuels in the Iberian Peninsula with the first industrial plant dedicated to the production of 100% renewable fuels from waste, in Cartagena (Spain). The company will start operations at a second plant in Puertollano in 2026. Additionally, Repsol will also launch a demonstrator e-fuels plant in Bilbao in 2026.
For more hybrid technology news, click here.
