Peugeot will unveil a concept version of a new diesel-hybrid powered 308 hatchback at next month’s Frankfurt Motor Show. Until now, most carmakers relied on petrol engines for their hybrid cars but it makes sense to use a diesel as the oil-burners are already more efficient than petrol motors. Peugeot’s new concept combines a diesel engine with an electric motor that’s said to improve fuel efficiency by up to 30% compared with the conventional diesel 308.

This means that the 308 Hybrid HDi will have a fuel economy figure of 69mpg (3.4L/100km) and a correspondingly low carbon-dioxide emissions level of just 90g/km. According to Auto Motor und Sport, the 1.6L turbodiesel engine will develop 109hp and 260Nm of torque, and will work in conjunction with a 22hp electric motor with peak torque of 130Nm.

The new hybrid model is planned for production and should arrive on the market in 2010 where it’ll be joined by a new flagship sedan with a six-speed transmission.