VW will do 100km on a litre

The diesel-hybrid coupe - an un-named development of the decade-old 1L (for 1.0 litres/100km) concept - is capable of less than 1 litres/100km (260mpg) yet can top 160km/h.

The refined version of the one-cylinder diesel-hybrid XL1 now has a two-cylinder diesel mated to an electric motor and has batteries that are charged both while driving and via a plug-in cord. Volkswagen last year showed the third version of the XL1 at the Qatar motor show. It was later caught testing the coupe in cold weather and this month was spotted in Spain for its warm-weather tests.

It is a further development of the 2011 XL1 concept that is a two-seater, and has its origins in the tandem-seat, single-cylinder 1L of 2002 that weighed just 290kg and claimed an astonishing 0.99 L/100km. Volkswagen updated the concept in 2009 as the L1 which retained the tandem seating but added a two-cylinder engine, effectively a Golf 1.6-litre turbo-diesel cut in half then mated to a 10.4kW electric motor.

It had a top speed of 160km/h, accelerated to 100km/h in 14.3 seconds and had emissions of 39g/km CO2. The latest XL1 is different again, now a plug-in hybrid that achieves 0.9 L/100km (260mpg) and CO2 emissions of 24g/km. The 800cc, two-cylinder turbo-diesel engine is rated at 35kW/121Nm and the electric motor
at 20kW/100Nm.

The two powerplants work together or separately and the XL1 can travel up to 35km on electric power alone. Its length and width are similar to the Polo - 3970mm long and 1682mm wide - but it is only 1184mm high. Volkswagen says the 2011 model has a governed top speed of 158km/h and accelerates to 100km/h in 11.9 seconds. In February, Volkswagen said it intended to build a limited series of XL1s starting in 2013.