Horse Powertrain, the Renault–Geely joint venture, has just given the internal combustion engine one of its strongest “not-dead-yet” headlines in years.
Together with Spanish energy company Repsol, it unveiled the HORSE H12 Concept: a 1.2-litre hybrid-oriented gasoline engine and powertrain concept designed to run on 100% renewable gasoline and to cut fuel consumption by around 40%, to below 3.3 l/100 km (WLTP), while reaching a claimed 44.2% peak brake thermal efficiency.
Close to diesel efficiency?
Those numbers are striking because they edge into territory traditionally associated with diesel engines. For decades, diesel has been the benchmark for efficiency in passenger cars, thanks to its higher compression ratios and lean combustion characteristics.
In Europe, especially, a diesel-dominated fleet consistently delivers lower CO₂ emissions because it consumes less fuel than comparable gasoline engines. Gasoline units, even modern turbocharged ones, typically lag behind in peak thermal efficiency.
The H12’s claimed 44.2% peak brake thermal efficiency, therefore challenging that hierarchy. While the very best gasoline hybrids have already crossed the 40% threshold in recent years, pushing beyond 44% brings a compact 1.2-litre gasoline engine uncomfortably close to traditional diesel territory.
In hybrid form, with an electric motor helping to keep the engine operating near its most efficient load points, the result is a WLTP figure of around 3.3 l/100 km, a consumption level more commonly associated with highly efficient diesel or advanced hybrid systems.
No match for electric
Yet even these impressive figures must be viewed in perspective. A peak thermal efficiency of 44.2% is exceptional for a gasoline engine, but it still cannot rival the fundamental efficiency of electric propulsion.
Modern electric motors typically convert around 90–95% of electrical energy into motion, with battery-to-wheel efficiency often remaining above 85%.
A combustion engine, by contrast, inevitably loses a large share of its energy as heat, no matter how advanced its design. The H12, therefore, does not challenge electric vehicles on pure energy conversion efficiency; instead, it represents an effort to push gasoline technology close to its practical thermodynamic limits while reducing lifecycle emissions through hybridisation and renewable fuels.
Consolidate assets
Horse Powertrain itself was created in 2024 to consolidate Renault’s and Geely’s combustion and hybrid assets into a global supplier capable of continuing development while many OEMs pivot heavily toward BEVs.
Renault and Geely each hold 45% of Horse Powertrain, with Saudi Aramco owning 10%. The structure reflects a technology-neutral approach to decarbonisation and electrification, where it makes sense.
But also continued investment in highly efficient hybrid powertrains and alternative fuels, where full electrification may be slower or less affordable.
Repsol, while not a shareholder, plays a crucial complementary role as a fuel and energy partner. Its involvement underlines that the H12 is not only about engine efficiency, but also about the decarbonisation of the fuel itself.
By developing and supplying 100% renewable gasoline for the concept, Repsol positions the project within a broader “molecules and electrons” strategy, where lower-carbon liquid fuels coexist with electrification rather than compete with it.
Next-generation hybrid demonstrator
The H12 was publicly unveiled only a few days ago and is positioned as a next-generation hybrid demonstrator rather than a production-ready engine tied to a specific vehicle.
Prototypes have reportedly been built and validated, and a demonstrator vehicle is expected in 2026. That places the technology beyond concept slides but still early in the industrialisation process, which includes years of durability testing, emissions certification, calibration, and cost optimisation.
Technically, the H12 is less a revolution in architecture than a refinement of every parameter that matters: high compression ratio, advanced combustion control, optimized turbocharging, and integration within a hybrid system designed to exploit the engine’s most efficient operating window.
The additional twist is the fuel strategy. The concept is designed to run on 100% renewable gasoline, aiming to reduce lifecycle CO₂ emissions without requiring large batteries or a fully developed fast-charging infrastructure.
Compared with established competitors, Horse is entering a mature and highly competitive field. Toyota and Honda have spent decades perfecting hybrid systems and control strategies, delivering consistently low real-world consumption across millions of vehicles.
Chinese manufacturers are also rapidly advancing hybrid efficiency with increasingly sophisticated systems. The real competitive test for Horse will not be a peak efficiency claim, but whether an H12-derived system can match or exceed rivals in everyday driving while meeting tightening standards such as Euro 7, and do so at a competitive cost.
As for timing, no Renault or Geely production model has yet been confirmed to use the H12. Horse has previously indicated that its broader hybrid system family targets mass production around 2027. If the H12 feeds into that roadmap, late 2027 or 2028 would be the earliest realistic window for first-series applications, assuming development proceeds smoothly, and a platform commitment is made.
