Tokyo green news: Mazda Sky concept

There's no car called the Mazda Sky Concept - rather, Mazda Sky is an actual concept: blue sky thinking, if you'll pardon the expression. Sky a theme, currently comprising a pair of engines and a transmission, each of which are designed to reduce emissions and fuel consumption. What else?

What's all the fuss about?

In lieu of a new concept to show off (although the Kiyora concept still looks as stunning as it did one year ago when it was debuted in Paris), Mazda is trumpeting its Sky technology, which consists of a diesel engine, a petrol one and an automatic transmission. They're called SKY-G, SKY-D and Sky-Drive respectively.

What makes it so green?

Mechanical adjustments that serve to reduce friction and aid lightness, in a nutshell. Friction losses account for a significant increase in fuel consumption; if you can make an engine or transmission's parts move more freely, less fuel is needed to keep them moving. It's that simple. The SKY-G petrol engine has 15 percent more torque than a non-SKY Mazda unit of the same 2.0-litre capacity, but uses 15 percent less fuel. The diesel is 20 percent more fuel conservative, and though together the engines make the Sky-Drive's five percent gains seems weedy, we're assured the performance of the auto gearbox is highly impressive too.

When can I buy one?

We're not sure yet, although the Kiyora concept on Mazda's plinth is fitted with a 1.3-litre SKY-G engine mated to a Sky-Drive transmission, which endow the car with 91.1mpg fuel economy. With a number as specific as that, it seems this tech isn't too far from production.

Mark Nichol