Mercedes-Benz, Volkswagen, Toyota, Nissan and Honda have all experimented with it, but Mazda is the first to actually do it.
The Japanese manufacturer's supercharged 2-litre SkyActiv-X petrol engine uses a form of compression ignition - like in a diesel engine.
Mr Hiroshi Tokushige, deputy general manager of Mazda Motor Corporation's powertrain development division calls it Spark-Controlled Compression Ignition. It uses very high compression - 16:1 - but still relies on spark plugs to ignite the fuel. This process is said to achieve better combustion.
"I am very sorry for writing such a super-complicated formula," he says through a translator, before showing journalists how the thermal efficiency of a piston engine is calculated and then explaining Mazda's objectives with SkyActiv-X.
According to him, the new unit produces 15 per cent more power, 10 per cent more torque, and 20 to 30 per cent better efficiency than the existing SkyActiv-G engine with the same 1,997cc capacity.
The new engine makes 190hp, 230Nm of torque and promises an average fuel consumption of between 4.3 and 4.9 litres per 100km. Even its 1.5-litre Mazda 2 hatchback burns more fuel than that.
The new engine's potential was noticeable in the SkyActiv-X prototypes, which I drove back to back with their SkyActiv-G predecessors at Mine Proving Ground.
The SkyActiv-X engines, with six-speed automatic and six-speed manual transmissions, were installed in current Mazda 3 hatchbacks with slightly modified bodywork, which accommodates not only the new engine but also new chassis and suspension components intended for next year's new 3.
Mazda Japan's global communications manager Hideyuki Saito says: "These are technical prototypes that still need fine-tuning, but you can feel the essence."
I felt it and it was mostly good.
The new engine is smoother, especially when revs went above 3,000rpm or so, and calmer while on a constant throttle. It also produces a stronger sense of acceleration, although more obviously with the manual gearbox than with the lazier automatic.
Most interesting of all, the engine's diesel-like torque pulls it up a slope in one manual gear too high, and with rev-counter hovering just above 1,000rpm.
The not-so-good aspects include a knocking sound from under the bonnet that only occurs with light throttle - during the lean-burn stage of combustion (indicated by a tablet attached to the dashboard of the prototype).
"We will fix the knocking sound issue by the time of mass production," says Mr Takehide Hoshi, Mazda's Asean PR manager.
The company has about a year left to perfect its intriguing diesel-like petrol engine before its official launch with the next-generation Mazda 3.
• The writer is the editor of Torque, a motoring monthly published by SPH Magazines.