BMW concept reportedly had 706mpg two-cylinder hybrid

We had assumed, when patent application photos of BMW’s dramatic new concept car leaked from Chinese corners of the internet, that we were looking at a very distant preview of the i5 – BMW’s much-awaited all-electric mid-sized saloon.

While the photos revealed a teardrop-shaped car that’s part Batmobile, part Stealth Fighter and all jaw-dropping, it perhaps didn’t look so unusual when you start to strip away the usual show car tinsel, and remember how oddball its closely related brother, the i3, looks.

Now though, it seems as if radical as the concept looks on the outside, that's nothing compared to what's under that skin. According to a BMW source quoted in Autocar magazine in the UK, the concept will feature a radical new powertrain that is set to be the next step in BMW's electric car armoury.

Realms of possibility

Not just batteries, and not the much-suggested hydrogen fuel cell, but actually a plugin hybrid range extender, with a tiny two-cylinder 1.0-litre turbo engine that returns a claimed 706mpg. No, there’s not a missing decimal point in that number.

It’s within the realms of possibility: after all, a well- driven Peugeot 208 diesel hatchback, without a hybrid battery or any special bodywork in sight, recently scored 141mpg on a MPG Marathon fuel consumption run, so three-figure consumption numbers are not beyond the ken of existing cars as it is.

Faster to charge

Then there are the batteries. The same nameless source told Autocar that BMW has developed some very new, very high-tech batteries for this concept, which have greater energy density and are also faster to charge.

Is it possible that BMW has made a breakthrough in the long-awaited field of lithium- air batteries? Or has it managed to find a way to make existing lithium-ion ones that much more efficient? Either way, it could be an intriguing step in battery technology.

Then there is the car’s construction. The still unnamed concept clearly draws on the lightweight aluminium and carbon technology developed for the existing i-car range, so its kerb weight should be very, very trim. Then, look at the view of the body from directly above.

Ignore the styling flourishes and flashes (which seem to suggest that legendary BMW stylist Chris Bangle may be back in action in Munich, or at least that some of his ideas are being resurrected) and look at the shape.

Classic teardrop

It really is a classic teardrop, almost a throwback to 1930s streamlined land speed record cars – it’s a shape that should slip through the air with an absolute minimum of fuss, disturbance and, yes, drag.

A figure of 706mpg would probably be still pretty unlikely away from the motorshow stage, from the laboratory or from the (cough, splutter) official fuel consumption tests, but once this concept has been through the production process and comes out the far end in a more realistic form, perhaps BMW might be able to claim 200mpg?

Maybe even 300mpg? And if you could get just half that figure in daily driving, that would be about three times as economical as an averagely driven 320d right now.