Debuted in the original Aygo in 2005, Toyota's 1.0-litre three-cylinder petrol engine is to become one of a new series of Toyota engines that achieve even higher fuel efficiency thanks to improved thermal and combustion management.

Under the changes, the engine achieves a maximum thermal efficiency of 37% – in combination with other fuel reduction measures this can deliver an improvement of almost 30% in fuel consumption compared to current vehicles (under the official Japanese test cycle).

Helped by the use of measures including a higher compression ratio than before and a lighter design, the engine has an estimated (pre-homologation) combined cycle fuel consumption figure of 68.8mpg, with CO2 emissions of 95g/km.

The first wave of Toyota's engines to feature these improvements also include a 1.3-litre petrol unit which uses the Atkinson cycle, a system previously adopted by Toyota for its latest-generation Hybrid Synergy Drive powertrains.

Worldwide, Toyota plans to introduce 14 new engine variations based on these units by 2015.