Diesels are at the top of the Dead Pool – on account of their particularly diesel exhaust byproducts, specifically particulates (aka, soot) and oxides of nitrogen (aka NOx). But diesels are much more fuel-efficient than gas-burning engines because they are compression ignition engines.
Well, compression and heat.
Instead of a spark to set off the explosion, the air/fuel charge is progressively squeezed (and thereby, heated) as the pistons ascends within its cylinder until – boom! – it ignites spontaneously.
More of the potential energy contained in the fuel is translated into useful mechanical energy.
This is why diesels go farther on a gallon of fuel than gas-burners.
But diesels also have the aforesaid emissions issues – also unique to their design.
Most of this – almost all of this – has been dialed out or tamped down or otherwise sequestered, notwithstanding the despicably exaggerated presentations of the media. Nonetheless, diesels are persona non grata, especially in the United States but increasingly in Europe, too.
There are outright bans – and if not bans, then regulatory rigamarole so stringent and expensive to comply with as to make it not worth complying with them.
Electric cars are touted as the alternative. But – again – the presentation is wildly misleading. They can only be the alternative if cost isn’t a consideration (which is like a woman getting pregnant at 60 without sex and hell, without a man involved at all) and only if large numbers of people are willing to accept not-minor functional inconveniences – in particular, the best-case scenario 30-45 minute wait to recharge the battery pack at a “fast” charger.
Which is as likely as expecting that people will put up with a 30-45 minute wait to get a cheeseburger at a “fast” food restaurant.
Mazda may have a better option: The diesel gas engine.
It won’t burn diesel fuel, of course. But it will diesel. That is, it will compression-ignite the air-fuel mixture. But it will also transition to spark ignition under certain conditions, the idea being to give the best of both worlds. This type of engine is called Homogenous Charge Compression Ignition – and Mazda says this will uptick fuel efficiency by 30 percent vs. an otherwise same-size spark-ignition engine.
And it will do this – so Mazda claims and hopes – without the soot and NOx emissions that have become politically problematic for diesel-burning diesel engines.
A side benefit will be more torque – something diesel-diesels have always had more of (and sooner) than spark-ignition engines.