What are you driving?
This is the SkyActiv-X version of the Mazda3 and, in spite of its relatively familiar looks, it's one of the most technologically advanced cars you can buy today.
That's because SkyActiv-X means that this 2.0-litre petrol engine burns its fuel a little like a diesel, and also a little like a petrol, with the idea that it can provide the best of both worlds - smooth, low-NOx petrol power and diesel-like economy and CO2 emissions are the targets. Mazda estimates that you should see a roughly 20 per cent improvement in your overall fuel economy, with peaks of maybe 30 per cent on certain journeys.
It works by squeezing the fuel-air mixture tightly, with a diesel-like 16.2:1 compression ratio. That's not - quite - enough to trigger compression ignition, as does a diesel engine, so the final kick is given by an extra squirt of petrol into the combustion chamber and a tiny spark to ignite the squirt. The subsequent heat from the burning fuel increases the temperature and pressure inside the cylinder to trigger combustion. That makes the combustion process inside the SkyActiv-X very economical, and very clean, not least because there's such as large proportion of air to fuel - it's like one of those Toyota Lean Burn engines from the 1990s, but even more lean.
To help with the economy figure, the SkyActiv-X also gets a mild-hybrid system so that its electrical energy usage is more efficient, and it can run a more aggressive stop-start programme when being driven around town.
The rest of the Mazda3 is as we know it in a technical sense, with a platform shared with the new Mazda CX-30 crossover, handsome styling, a high quality cabin, seats that purport to put your spine into a more natural position and high-end safety kit that includes a driver monitoring system that can tell when you're not looking at the road, and remind you to do so.
Name its best bits
If you haven't already made up your mind about the Mazda3's styling from the photos, then let us put in our own two cents - it's gorgeous. Arguably not quite as hopelessly handsome as the Mazda3 hatchback (saloons almost always tend to look a little staider than five-doors), but still hugely good looking. The low-hanging, almost anteater-like, snout is copied over from the hatch, but at the back the saloon bodywork also means a less heavily angled window line, so rear-seat visibility and light levels are improved compared to the slightly claustrophobic five-door. Worth bearing in mind.
In the cabin, Mazda is continuing with the relatively pared-back cabin design that it first pioneered on the RX-8 sports car, but here in the Mazda3 the materials feel much richer, and so it's a real quality piece. As demonstrated in the updated Mazda6, the Japanese company can create a cabin to compete with the premium Germans in quality terms, and the 3 simply brings that performance down a size category. Comfort is excellent, too - those seats are really good.
As with pretty much every generation of Mazda 3, this one is also a delight to drive. The steering has a slightly light weighting to it, but plenty of feel and feedback reaches your fingers, and the chassis follows your inputs with a delicate fealty. Only a slightly stiff ride quality detracts from the dynamic performance.
Anything that bugs you?
The thing is that the SkyActiv-X engine could appear in either the 'best bits', or the 'bugs us' categories, but because we have some question marks over it, it goes at least into the 'doubts' column.
The technology is fearsomely clever, and Mazda has created an engine that seamlessly combines diesel and petrol-style combustion without ever letting the driver know. At very low speeds, with the stereo turned off, you might occasionally pick up a faint, distant sound that mimics a diesel rattle, but it's barely noticeable.
The problems with the engine are twofold. One, performance is still pretty pedestrian, at least to those of us who've become used to the low-down kick of turbocharged engines. The maximum of 180hp is a very healthy power output and, if you rev the 3 hard, it does pick up and go, but the rest of the time it feels languid at best.
Two, the fuel economy is variable. On some journeys, we saw excellent consumption numbers - as low as 5.8 litres per 100km on one run, which is deep into diesel territory. On others, it was nowhere near as good, sometimes falling the wrong side of 10 litres per 100km on short urban runs, and ultimately our overall figure was a slightly disappointing 6.8 litres per 100km, or 41mpg.
That's a figure we actually bettered in a standard, and much more affordable, 122hp Mazda3 SkyActiv-G (naturally aspirated petrol with normal spark ignition), so the cost of upgrading to the SkyActiv-X is questionable.
And why have you given it this rating?
The core Mazda3 is an utterly excellent car, easily the best-looking hatch or compact saloon in its class, and right up with the very best when it comes to steering and chassis. The SkyActiv-X engine is technologically advanced, very clever and smooth, but there are question marks - for now - over its economy.
What do the rest of the team think?
The Mazda3 makes even more sense in practical saloon guise. I love how it drives and the interior quality. Like Neil, though, I have serious reservations about the claims made for this new engine. I didn't find it any more economical than he managed and hence I'd stick with the regular petrol option instead if it was my money.
Shane O'Donoghue - Editor
Like Neil, I too have my doubts over just how good that SkyActiv-X engine, and spending a week with it I ended up with an average of 5.9 litres/100km, though that's not far off what I would have gotten with the regular petrol version of the Mazda3 hatchback. Engine aside, the saloon is a very handsome thing, and the interior quality seems top notch. Worth the extra if you fancy something a little different.
Dave Humphreys - Road Test Editor