The debate about the future of the combustion engine has been on the table for years, but now it returns stronger than ever. Although most manufacturers are firmly committed to electricity, a few—but very strong—are pushing to keep traditional combustion alive. And they have achieved something important: that Brussels relaxes the rule that prohibited the sale of thermal cars from 2035.

It is advisable to clarify what exactly happened, because it is not a simple extension. In December 2025, the European Commission proposed replacing that total ban with a 90% reduction in emissions in 2035, offsetting the remaining 10% with low-carbon steel manufactured in the EU, e-fuels either biofuels. In practice, this keeps alive the plug-in hybridsmicrohybrids and even some thermals beyond 2035. Of course, it is still a proposal that Parliament and the Member States have to approve.

The backdrop is always the same. Electric mobility is more expensive, and the Chinese market has a considerable advantage: a lot of technology and, above all, much lower prices. For many, abandoning combustion suddenly, with today’s technology and resources, is rolling out a red carpet to the Asian giant. It is a matter of time before, once the wall of consumer confidence is torn down, Chinese manufacturers gain weight in the market.

One of the brands that is very clear that the combustion has more life left than what is said is Mazda. That is why it has been searching for years for formulas that comply with emissions regulations and give a second youth to the thermal engine. He already tried it with him SKYACTIV-Xthe controlled compression ignition (SPCCI) gasoline engine it launched in 2019 to squeeze near-diesel efficiency from gasoline. And now it is involved in something much more ambitious that, if it overcomes all the challenges, could fuel the debate even more.

Mazda’s six-stroke engine

Mazda is developing a six-stroke engine that is greatly surprising an industry that looks askance at it. To understand it, you have to start from the classic four strokes—intake, compression, combustion and exhaust—which Mazda does not eliminate: it preserves them and adds two more phases.

In the fifth stage, instead of expelling the exhaust gases, it diverts them towards a special catalyst, the decomposewhich works like a conventional catalyst but without precious metals such as platinum. A small extra amount of gasoline is injected there and, with the heat, a reaction occurs that separates the carbon from the hydrogen: the carbon is trapped in a solid state and the hydrogen is released.

In the sixth stage, that hydrogen is reinjected into the cylinder and expands, generating additional energy and closing the cycle. The result is that, in essence, the engine ends up burning hydrogen: water vapor comes out of the exhaust, while the carbon is stored in a tank.

When that tank is full, it must be emptied, just like refueling with gasoline, only in this case it is to remove solid carbon instead of adding fuel. And if the internal hydrogen tank runs empty, the engine can return to operating in the traditional four-stroke cycle, which would make it compatible with the current infrastructure without any external adaptation.

Mazda’s objectives (and challenges)

Mazda’s carbon numbers are not exactly low. A vehicle the size of the CX-5, which is used as a reference, could accumulate up to 38 kilograms of solid carbon for each tank of gasoline consumed. This requires designing an entire infrastructure to collect and manage this material at gas stations.

The good part is that this carbon is practically pure and could be reused in industry – for example, to make steel or pigments – instead of ending up in the atmosphere.

The mechanics, yes, are a huge challenge. Many more injectors, new valves, electronic actuators and that additional catalyst are needed, and all in one of the most crowded areas of an engine: the cylinder head. In addition, the propeller loses power when working in six-stroke mode, so the patent itself proposes combining it with an electric motor to compensate.

And the big question remains: efficiency. All that intermediate conversion can penalize overall performance, something that will only be known when there is real operating data. Because it’s worth not forgetting: for now this is a patent, not a car you can buy.

The strategy: don’t bet everything on one color

This engine is a good example of Mazda’s strategy: not to risk everything on a single technology. While not losing sight of the reality of the market and the progress of the electric car, he continues to defend that combustion has a lot of life left, as long as emissions are reduced.

But at the same time it works on batteries, electric and hybrids. In fact, it already has a date for its new combustion engine, the SKYACTIV-Zwhich will arrive at the end of 2027 in the new CX-5 accompanied by the first hybrid system developed entirely in-house by Mazda (until now it used Toyota technology in models such as the CX-50).

The SKYACTIV-Z is a 2.5-liter four-cylinder designed for almost perfect combustion – what Mazda calls “lambda 1” – and to meet the demanding Euro 7 and Tier 4 standards without sacrificing performance. And the brand does not stop there: it even keeps alive its hallmark, the rotary engine, now converted into a generator for hybrids.

In short, Mazda does not bet everything on one color. And its underlying message is increasingly shared in the sector: combustion and the electric car are going to coexist for much longer than many thought.