Mazda’s new SkyActiv-X engine will go against every convention you thought you understood about gasoline engines. It’s supercharged, but for efficiency purposes, not to increase power. It has a compression ratio of 16:1 (in current prototype form) yet runs on 87 octane fuel. It relies on the Miller cycle (or modern Atkinson cycle) when it wants to make power, yet runs a traditional cycle, albeit with compression ignition, when it wants to be efficient. It’s a gasoline engine that encourages knock, but in a controlled manner… What?

It sounds confusing at first, and unfortunately the complications accumulate as you dive deeper. Mazda is doing something nearly every auto-manufacturer has thought about, researched, and certainly desired, but they did it all with the help of a spark plug. Spark Controlled Compression Ignition (SPCCI) is a new method of combustion that allows gasoline engines to run on compression based ignition. In other words, it takes the combustion methodology of a diesel engine, while using the timing methodology of a spark-ignited gasoline engine.