Mazda's SkyActiv technology is a suite of developments aimed squarely at reducing the small Japanese automaker's carbon emissions. Given that the new Mazda3 can get up to 40 mpg highway, it seems to be doing pretty well.
This, however, is only the beginning. Mazda has let some details slip regarding the second generation of SKyActiv engines, and the company is promising a 30% improvement on fuel economy, and carbon emissions equal to electric cars. No, this doesn't mean zero emissions, they're factoring in the coal burned to charge the electric car in the first place. The new system is a mash-up of the way both gas and diesel engines run, optimized for gasoline.
A third generation of SkyActive engines is also in the pipeline, that will keep as much heat as possible in the engine, and should provide another efficiency boost of about 30%. Mild hybrid systems might start to appear in 2020, but there are no definite plans yet.