Mazda's best surprise unveiled at this year's Tokyo Motor Show is neither of its two concept cars, stunning as they are.

It is Skyactiv-X, the carmaker's new engine, the first commercial petrol engine that utilises high compression to ignite the fuel-air mixture - just like a diesel engine, which works without spark plugs.

Hence Skyactiv-X combines the benefits of a petrol motor (smoother and higher horsepower) with the advantages of a diesel engine (higher efficiency and greater low-end torque).

Mazda's current Skyactiv-G petrol engines have a compression ratio of 13:1, or 13 parts air to one part of petrol. The carmaker says that the new Skyactiv-X engine will exceed this ratio, but citing confidentiality issues, did not provide figures.

Mazda claims that a Skyactiv-X engine, compared to a Skyactiv-G engine of similar displacement, will improve fuel economy by 20 to 30 per cent, while producing 10 to 30 per cent more torque.

Mr Ichiro Hirose, who is in charge of powertrain development at Mazda, talks to The Straits Times about the company's latest brainchild, as well as the company's future powertrains.

How long has Skyactiv-X been in development?

It has been two years since we started. But we will launch it only in 2019, so total development time is four years.

Skyactiv-X uses higher compression ratios compared to Skyactiv-G. What is the minimum octane fuel it requires?

Usually, high-compression engines require higher octane to prevent premature detonation, which is known as "knock". However, Skyactiv-X takes advantage of this "knock", so the lower the fuel Research Octane Number (RON), the better the fuel economy.

That said, we designed Skyactiv-X to use a minimum of 91 RON. This type of fuel is more widely available not just in the Asean region, but globally too.

After 2025, all new Mazda models will either be petrol-electric hybrids or full electric. Will the latter have range extenders?

Our first full-electric vehicle will be introduced in 2019, and it will have a range extender, which will be a rotary engine.

How big will this rotary engine be?

Right now it is a secret.

What minimum range can we expect from the pure electric vehicle?

We're still considering this. The range will also depend on how advanced battery technology will be.

With various electric cars, no matter the brand, the driving experience feels the same since electric motors deliver instant torque. How will Mazda differentiate its models?

We will ensure that our electric car follows the jinba ittai ("horse and rider are one" in Japanese) handling philosophy, so that it stands out.

• The writer is with Torque, a motoring monthly published by SPH Magazines.