YOU'LL search in vain for a diesel version of the latest Mazda3, even though one was listed on the car's launch here in the spring.

But the reason for the demise of the diesel isn't because the fuel is a dirty word in politicians' mouths - but because Mazda reckons it can do better with petrol.

More specifically, with the clever petrol engines now offered in the Mazda3 as rather pricier alternatives alongside the existing line up of petrol powerplants.

The cleverness comes from technology Mazda calls spark controlled compression ignition (SPCCI), which mixes conventional petrol engine technology with a touch of diesel cleverness to produce better economy and emissions.

Ask for maximum power and the 2.0 litre engine act like a normal petrol unit, where the spark plug sets off the fuel and air mixture in the car's four cylinders.

But row back on the throttle (which means most of the time in a typical drive) and the engine turns clever enough for Mazda to claim a world first for this technology in a petrol engine.

In essence, the spark plug ignites a tiny ball of fuel rich mixture which expands so fast the rest of the much leaner mixture in the cylinder ignites itself, as happens in a diesel engine.

If that explanation sounds a bit technical the resulting improvements in economy and tax reducing emissions are much more down to earth.

So, the new engine produces 177bhp against the 120bhp of the current (and continuing one) but fuel economy under tougher and more real world WLTP test is as good as 51.4mpg compared to the 45.6mpg of the older engine.

Company car users will be happy to see tailpipe emissions drop from a best of 117g/km to 96g/km and BIK tax bands fall from a worst of 29 per cent to a best of 23 per cent.

The improvements are enough to convince Mazda it no longer needs to offer diesels in this range, although they remain available in some other models.

Moving from a Mazda3 with SkyActiv-G engines to the new SkyActiv-X technology adds around £2,000 to the bottom line.

But consider that the huge majority of new cars are bought on a PCP deal and the increase comes to around £27 more a month - which then sounds eminently affordable.

Prices for the SkyActiv-X versions of the Mazda3 start at £23,555 and stretch to £31,295 for a version newly fitted with all-wheel drive, which may be a rare order in this hatchback but will seem a fine fit for the upcoming CX-30, a Mazda3 derived SUV destined for these shores in a few months.

Also available with the new engines is a Mazda3 saloon, sharing only bonnet and windscreen with the hatch and identically priced.

Its boot packs 444 litres of loadspace compared to the 358 litres of the hatch, thanks to an extra 200mm length in the body behind the rear seats. But fold the hatch's rear seatback flat and luggage room vaults to 1,026 litres.

But back to the new engine. If you hadn't been told about the newfound cleverness the Mazda3 would continue to feel like a lively machine with a hint of sporty directness to the steering and gearchange - and combined with a ride that can hint at harshness on some surfaces, especially if the car is equipped with big 18ins alloys and not the smaller 16ins rims of cheaper versions.

Alerted to the technology going on under the bonnet and at low speed on a smooth road you can just detect a bit of diesel detonation. But only a bit.

Pushed to extremes the new engine provides the Skyactiv-X with a 134mph top speed and zero to 62mph in 8.2 seconds - so it's a pleasantly responsive machine.

More impressive still was a dash readout of 47.3mpg after a decently varied workout on a mix of roads. Good enough, you'd reckon, for Mazda not to worry about ditching the diesel.