VOLKSWAGEN has its Golf, Toyota has its Corolla and now General Motors has its Cruze – critical small cars that are pivotal to the health of these global auto giants.

But no car is more important to a mainstream car company than the Mazda3 is to Mazda, which depends on the four-cylinder sedan and hatch range for about 80 per cent of its global volume.

More successful in Australia than anywhere else in the world, Mazda has ridden the Mazda3 (nee Mazda 323) to the top of the small-car market in Australia, where more than 250,000 customers have fallen under its spell of spunky styling, Japanese quality, trustworthy engineering and perceived value.

Apart from its well-deserved reputation for fine fit and finish, the Mazda3 has never really been a leader in any memorable area, except where it counts – on the sales scoreboard, where it has not only outsold its small-car rivals this year but, as we write, the market leader for 15 years, Holden’s Commodore.

Now, however, the Mazda3 has bragging rights in at least one key area: it is the most fuel-efficient petrol car in its class, returning an official combined fuel consumption reading of 6.1 litres per 100km.

This pips the 6.2L/100km of its first cousin, the new EcoBoost-equipped Ford Focus. Or, at least, one new Mazda3 variant does: the SP20 SkyActiv.

While other variants in the just-refreshed Mazda3 range lumber on with previous-generation MZR four-cylinder petrol and diesel engines, the $27,990 Mazda3 SP20 hatch and sedan get Mazda’s newest SkyActiv-G engine technology that – along with a matching new SkyActiv six-speed automatic transmission – is claimed to cut fuel consumption by 25.6 per cent over the 2.0-litre engine still used in the Neo and Maxx Sport models.

As Mazda’s global standard bearer, the Mazda3 was selected to bring this new technology to market, ahead of a wider and more thorough rollout in all-new vehicles such as the CX5 compact SUV due in the first half of next year and the Mazda6 to follow.

Mazda claims the new technology not only makes its cars more efficient but quieter and more drivable.

Producing 113kW at 6000rpm, the normally aspirated, high-compression 2.0-litre direct-injection SkyActiv engine is no power sensation and it is difficult to discern any great improvement in acceleration over the base Mazda3.

While torque is said to have been enhanced across the range, the torque curve reaches its zenith at a lofty 4100rpm, which means maximum grunt does not often come into play.

It was telling that no claimed 0-100km/h acceleration figures were provided in the media kit.

As with Ford’s rival EcoBoost engines, perhaps a small, low-boost turbocharger would transform this engine.

Rather than enhance the driving experience, the new-six speed automatic transmission blunts any sports leanings of the engine by resisting kick-down and holding gears like a rugby player clutching the ball in a tackle.

Of course, this is all about saving fuel – going green carries a cost.

Fortunately, the transmission has a manual mode, allowing the driver to bypass the transmission’s electronic nanny on curvy roads. Unfortunately, there are no steering-wheel mounted gear-change paddles, so it is all a bit clunky and pointless.

It seems that the ‘SP’ in SP20 now stands for ‘standard performance’, not ‘sports’, and like so many fuel-saving cars, it is a cruiser, not a bruiser, and that is where it excels.

We averaged 5.9L/100km in several hours of mainly highway driving, giving some credibility to Mazda’s claim of 6.1L/100km urban-highway.

While we didn’t come to a rest at traffic lights too often, we did get to sample Mazda’s first idle-stop system and marveled at the ingenuity of the engineers who dreamed up the idea of restarting the engine, not by conventional starter motor, but by stopping the engine with one cylinder all primed with fuel and ready to fire with a single spark. Is that clever or what?

The SkyActiv-G figures fall a little short of diesel performance at the pump, but not by much. And besides, filling up with conventional 91-RON petrol would appeal more to your typical small-car buyer than smelly old diesel, while the SkyActiv engine is immeasurably quieter as well.

Over the years, Mazda cars have become known for droning road noise and not-so-subtle bump absorption on our harsh Australian roads.

Mazda has gone a fair way to address these issues in the facelifted Mazda3 and, while it is not the quietest or fluffiest ride around, the car we drove at the launch was noticeably more refined from the tyres up.

This new-found refinement is helped by the quieter powertrain, at least in its usual cruising mode. At higher engine speeds, the engine becomes a little thrashy. We searched in vain for the claimed tasty new exhaust note, but it sounded like a Japanese four-cylinder to us.

The Mazda3 has been widely regarded in the public realm as a zippy little hatchback and while its steering and cornering abilities have not always kept Volkswagen or Renault engineers awake at night, the average driver has had few complaints.

Like the road-noise suppression and improved ride, the steering of the latest Mazda3 has come in for some attention, with tweaks to make the transition through the bends more agreeable.

Light and easy, the steering gives reasonable feedback through the leather-clad steering wheel, while delivering pleasing turn-in bite, tending to understeer when pushed. In other words, competent front-wheel-drive small-car point-and-shoot.

Most of the remainder of the Mazda3 is carried over – brakes, interior layout, boot space and so on.

Inside, we like the new white-on-black speedo and tacho presentation, replacing the odd orange-on-black used by Mazda for yonks, for reasons lost in the sands of time. The SP20 gets a blue wash of light around the edge of the dial (and around the headlights, too) to signal its enviro pretensions.

But we aren’t so keen on the small LCD data screens mounted at a distant spot in the dash.

The lower-range models get some appealing fresh seat fabrics and all Mazda3s retain the soft-touch interior surfaces that this car-maker does so well.

The exterior styling comes in for some spit and polish, with a new smiley face and bobbed tail. The latter carries a blue-hued SkyActiv badge on the SP20 variant, which – apart from the drivetrain – is based on the second-rung Maxx Sport model.

Considering the Maxx Sport automatic sells for $26,490 (plus on-road costs), the SP20 buyer is effectively paying about $1500 extra for the new powertrain (which includes an extra cog in the auto trannie).

The car we drove was equipped with the optional $3000 Luxury pack that adds – among a range of nice-to-have extras – leather to the cosseting seats that accommodate five, as long as the three across the rear bench are kids.

But we have saved the best news about the new Mazda3 for last: each model is cheaper, better equipped and more refined than the last.

At $27,990, the SP20 SkyActiv is more affordable than many pundits thought it would be and, while sports hatch buyers should look to other models such as the big-bore SP25 or turbocharged MPS, the SP20 would satisfy the needs of most small-car buyers.

Especially each time they fill up.