KIA has a new eco champion with its latest Rio diesel supermini.

Drive it down to the city from which it takes its name and - in theory - a round trip from London will soak up around £750 in fuel.

And the significance of that soiree to the Brazilian carnival capital is that it's about the same distance as the average annual mileage completed by drivers in Britain.

Do the math, as they say, and that shakes down to a weekly fuel bill of less than £15.

On paper the all-new Rio 1.4-litre diesel has an official fuel return of 81.2mpg and even when put through its paces in everyday conditions it shapes up well.

The new Rio will be arriving in a matter of weeks and the 10 model line up is priced from £11,995.

The diesels start from £13,495 and the high grade trim level Rio 3 CRDi we tried comes in at £17,245.

In this specification the engine is uprated from 76bhp in the lower grade versions to a livelier 89bhp and that knocks official fuel consumption back to 74.3mpg with a CO2 rating of 98g/km.

Nevertheless, on a good run around the Thames Valley just outside London the Rio acquitted itself in handsome fashion showing an average of 65mpg after a two hour trip at an average speed of 35mph.

Not bad at all from a compact hatch which is now not as small as before.

The latest Rio has grown up in every way to become a genuine alternative to the likes of a Ford Fiesta or VW Polo.

Compared to the previous model launched back in 2011 the new Rio is slightly bigger inside and out, can seat four adults in comfort (as in all superminis five is a squeeze) and comes with a decent sized boot of 325 litres.

The fourth generation of Kia's global top seller now comes as a five-door only and looks all the better for it.

There's a restyled front with a new-look to the apron, headlights and grille and the door mirrors have been resited to sit higher.

All versions come with air conditioning, front electric windows, Bluetooth connectivity plus USB ports front and rear (unusual in this class of car) and LED daytime running lights.

Level 3 trim is big on specification and includes sat nav, a seven-inch touchscreen that now stands slightly proud of the facia and leather-effect upholstery.

It is smart and contemporary and also features a full smartphone interface, heated front seats and even a heated steering wheel. On the safety front there's automatic emergency braking and lane departure warning.

Top speed in the higher powered 1.4 diesel is 108mph with 0 to 60 acceleration of 11.6 seconds while the 76bhp version takes 13.5 seconds and tops out at 102mph. Both are six speed manuals.

On the road it is impressively quiet, especially for a diesel, and as well as an array of electronic traction and stability controls the new Rio comes with what Kia calls ‘straight line stability' which keeps the handling tidy when cornering.

The driving experience is all nicely composed and the Rio feels sturdy, safe and sure - a little car with big car credentials if ever there was.

Factor in those fuel-sipping characteristics and Kia's seven year warranty and the Rio diesel makes a lot of sense as a proper little family car that's ready to lap up the miles.