Road Test: Fiat 500 0.9 TwinAir 105 Lounge 3dr

Fact! The 500 TwinAir is the greenest petrol car in the world. Wait! Before you file it in that Dull But Worthy shoebox, hang on. Such greenness is achieved because the TwinAir is powered by a two-cylinder engine, just like the original 500 back in 1957.

A twin! In a 500! To be precise, it’s an inline two, displacing 875cc and developing, in the turbocharged form seen here, 84bhp – a naturally aspirated 64bhp and warmer 104bhp turbo version will follow. With Fiat’s MultiAir timing and stop-start tech, the twin 500 will return a claimed 69.9mpg and emit just 95g/km of CO2: cleaner than a Polo BlueMotion, cleaner than a Honda Insight.

Enough numbers. You want to know how it sounds. If you’ve got the manically popping, staccatoed stutter of an old-school British bike in your head... sorry. Aside from a puttering noise below about 1,500rpm, the TwinAir 500 isn’t hugely engaging in the ear department: largely hushed, a bit droney at high revs, but no worse than the 500’s existing 4cyl petrol.

The TwinAir is, for such a dinky engine, amazingly refined and smooth. If you’ve had the misfortune to drive the three-cylinder Corsa from the mid-Nineties, you’ll know how binary few-cylindered engines can be. The TwinAir, though, is thoroughly linear in its responses, picking up easily from low revs and delivering a nice spread of power.

Maybe, if we’re being picky, it’s a bit too grown-up. We had visions of a whipcrack bike engine, fizzing up to high revs with featherlight flywheel response, but the TwinAir is nothing like that. Fiat’s engineers have clearly worked hard to banish the Twin’s two-cylinder character in favour of relaxed, easy-drivin’ manners.

Even though the TwinAir won’t be the cheapest 500 when it goes on sale here in September – prices are expected to start around £1,500 more than the entry-level 1.2-litre four-pot petrol – its driveability and awesome economy will make it the Cinq of choice. And this engine represents just the start of Fiat’s two-cylinder plans: a petrol-electric hybrid version should enter production in the next year or two.

For now, the guys at Fiat should be applauded for a cracking piece of engineering. The TwinAir offers a brilliant prospect in an era when small-displacement engines have become virtual clones of each other. Just imagine what it’ll sound like when Abarth gets its hands on it…