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As sure as you are reading this, I still remember the day, decades ago, when my uncle tried to imagine how great it would be if you could combine the benefits of a petrol and diesel engine.

He was that way inclined; always madly interested in engineering and mechanics and imagining how things did, and could, work.

I wondered that sunny day down on the farm if he was even ‘madder’ than I thought.

He wasn’t.

He was just ahead of his time in his thinking and imagination. He certainly engendered a wonder in me about the mechanical magic that is the internal combustion engine.

And I felt a tinge of regret recently over how I reacted and told him his petrol/diesel combination was impossible. Because it isn’t.

Mazda have just done it.

They have mixed the spark characteristics of a petrol car with the compression associated with a diesel.

As you know, a petrol engine uses a spark to ignite the air-fuel mixture in the cylinder of the car.

A diesel, meanwhile, compresses the mix so that it explodes. Combine the two methods and you get petrol being burned under high pressure and with a spark stoking the fires.

It has taken a long, long time to make it to market on a commercial basis. And I have just been driving it.

I think Mazda should have called it a Petrodiesel or something to give you a more immediate clue to its unique power source.

Instead they distinguish the Spark Controlled Compression Ignition technology (SCCI) with a ‘Skyactiv-X’ name which always and ever reminds me of satellite TV.

Anyway, this Skyactiv-X model emits 102g/km or 103g/km (saloon/hatch) and incurs €190 road tax.

Not bad at all on paper (and I stress on paper) for any 2-litre – be it of petrol or diesel persuasion that develops 180bhp.

It debuts in Mazda’s new ‘3’ hatchback and saloon. I’ve already briefly tested it in Bulgaria but my consumption of 8.2l/100km would not be a reflection of its latent frugality, Mazda claim.

Their average is 4.5litres/100km – thanks in small measure to the having a 24v mild-hybrid system.

It is quite a consumption gap to close so it was a matter of driving and seeing how I got on under longer and more varied driving conditions in Ireland.

Before reporting that, it might be worth mentioning the saloon on test was a much different car to the hatch previously driven: only the bonnet and windscreen are similar. They have the same wheelbase, but the saloon is 200mm longer and has a decently accessible 444-litre boot which got plenty of work.

As I hadn’t previously driven the saloon, I have to say I was impressed. It’s a more imposing car altogether. I liked the shape of it. There was a real substantial feel to it when I sat behind the wheel.

As I drove it for the first time here, I could picture myself chatting with the uncle about how, under this system, air and fuel are compressed to a high level. The spark plug starts a tiny fireball which ups the temperature. In doing so you get greater fuel efficiency and there is a reduction in NOx emissions.

Naturally there is a premium for the technology but the package has to make financial sense surely. One of the few ways of doing that is to create lower fuel consumption. Even at that, you’d still have to fill a lot of tanks of petrol to justify my top-spec version on test: €37,270.

The initial portents were not good; 10-litres to the 100km at one stage, according to my on-board computer, in town driving. That steadily improved to 7.7l, 7.1l and ultimately 5.7 (and falling) after country runs.

My drives, by the way, yielded a couple of non-consumption related criticisms. The tyres fed through a fair bit of road noise and I was seriously disappointed at the lack of pulling power in fifth and sixth gears.

Neither was the engine as smooth as I’d expect from a 2-litre petrol.

But the car oozed class; from the smooth, chunky lines to the materials used in the cabin; even the tone of the indicator (I kid you not, it was one of the first things I noticed) spoke volumes about the attention to detail.

So would I buy it? Yes, I would – for the car and the technology but not for the price or the moderate fuel consumption.

Facts & figures

Mazda3 Skyactiv-X:

2-litre, petrol, 180PS, 6spd, 4.6/5.6l/100km, €190 road tax; 24v mild-hybrid system. Car tested €37,270, Skyactiv-X from €30,920. Range from €28,320.

Platinum Sport tested; Advanced Safety Pack; includes stone leather interior, rear camera, CD player, 12-speaker Bose system, 360˚ view monitor, cruising/traffic support, front-cross traffic alert, rear City Brake support.

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