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Is a diesel engine that burns gas the holy grail?

Mazda thinks you'd rather wrap your head around this than a plug.

Now playing: Watch this: Engine holy grail: Gas, diesel or electric?

I received an email from Kristopher C. in Barbados asking if Mazda's Skyactiv-X engines are the next big thing or just the next fascinating oddity? 

Skyactiv-X engines use gasoline but combust it like a diesel with high compression and temperature instead of using a spark plug. That arrangement, called homogeneous charge, means you get more energy out of each drop of fuel as well as the lower emissions that come from burning gasoline. Mazda quotes about a 30% bump MPG and torque. Sounds like the holy grail, right? Almost.

The Skyactiv-X engines still have spark plugs and the related wiring and timing electronics because it proved impossible to manage diesel-style combustion with gasoline at very low or high RPMs. Frankly, it's a miracle they could make this work at all given gasoline's touchiness when highly compressed. 


Mazda has made a lot of cuts against the grain over the years. Some, like Miata, are absolute home runs while others, like rotary engines, were mostly pushing a rock up a hill.


But the bigger question is whether Mazda is frittering away R&D on combustion when they should be focused on electrification? Skyactiv-X took many years to develop and arrives just in time to meet several countries' and California's plans to ban combustion engines in the foreseeable future - Norway by 2025. Combine that with the fact that states like California already require carmakers to sell a percentage of zero emission vehicles (and for all its technical prowess, Skyactiv-X ain't that) and you can see why I think Skyactiv-X is an amazing technology but not the next big thing.

Mazda will tell you that they have their electric bases covered by a recent partnership with Toyota and Denso. To my mind, that marginalizes Skyactiv-X more than buying it breathing room. Like them or not, regulations and subsidies are forcing the industry toward electrification.

Even highly-accepted diesel engines are falling out of favor in Europe, and several major carmakers have signaled a retreat from them due to the stubborn problems with the NOx emissions. BMW is not one of those, however, almost bearing a conspiracy theorists ire at diesel's downturn. "For almost two years now, diesel technology...has been deliberately and publicly discredited," said Harald Kruger, BMW CEO and Chairman. 

In what might be another bit of flat timing, Mazda is just about to bring diesel to its U.S. line with the 2017 CX-5. Skyactiv-X engines are expected in showrooms in 2019, likely in the next Mazda3.