Mazda's new range of Skyactiv-X engines under development are set to replace the current Skyactiv-G range in 2019. They use compression ignition technology that has previously only been used in diesel engines. The Japanese carmaker claims an efficiency improvement of 30 percent over current petrol units, matching or even improving on the brand's Skyactiv-D diesel engine range. Mazda said this will enable Skyactiv-X engines to produce lower CO2 emissions than electric drivetrains from a 'well-to-wheel' perspective - which accounts for the whole life cycle of a vehicle and the fuel needed to power it. Mazda has been developed the new technology for several years, as first reported by our sister publication, Autocar UK, in 2014. Compression ignition technology has not yet been used on a mass production scale in petrol engines.