The first prototypes for the 2019 Mazda 3 have been spotted this week, with exterior graphics indicating the company's new SkyActiv-X compression-ignition petrol engine is hitting the road too.

Interestingly, the matte-black vehicle in the images is a pre-facelift version of the current-generation Mazda 3, while the wheels are borrowed from the updated model currently on sale.

What gives the prototypes away, other than the matte-black exterior finish, is the 'SkyActiv-X' lettering on the sides, referring to the new compression-ignition petrol engine technology the company plans to release in 2019. Clearly, this is one prototype that won't have engineers gesticulating wildly at spy photographers.

How does it work? High-efficiency compression ignition means the fuel-air mixture ignites spontaneously when compressed by a piston.

It’s a proprietary combustion method called Spark Controlled Compression Ignition, which Mazda claims maximises the zone in which compression ignition is possible, and yields “a seamless transition between compression ignition and [traditional] spark ignition”.

Mazda says the technology improves engine efficiency by up to 30 per cent over the current SkyActiv-G petrol engine family, while achieving similar fuel economy to its SkyActiv-D turbo-diesel engines.

The new engine has been confirmed for a 2019 global launch, in line with the introduction of the next-generation Mazda 3.

It's believed full-body prototypes for the next-gen Mazda 3 should start hitting the road in around six months time, so stay tuned to CarAdvice for more updates.

Click the photos tab for more images

NEWS: Mazda launching compression-ignition in 2019