The Volkswagen XL1 (VW 1-litre) is a two-person limited production diesel-powered plug-in hybrid produced by Volkswagen. The XL1 car was designed to be able to travel 100 km on 1 litre of diesel (), while being both roadworthy and practical. To achieve such economy, it was produced with lightweight materials, a streamlined body and an engine and transmission designed and tuned for economy. The concept car was modified first in 2009 as the L1 and again in 2011 as the XL1. A limited production of 250 units began by mid 2013 and pricing started at (~ ). The Volkswagen XL1 plug-in diesel-electric hybrid was available only in Europe and its 5.5 kWh lithium-ion battery delivered an all-electric range of , had a fuel economy of under the NEDC cycle and produced emissions of 21 g/km of . The XL1 was released to retail customers in Germany in June 2014. History Prototype The prototype VW 1-litre concept car was shown to the public in April 2002 when Ferdinand Piëch, then chairman of the board of management, drove the concept between Wolfsburg and Hamburg as part of the Volkswagen annual meeting of stockholders. For aerodynamics, the car seats two in tandem, rather than side-by-side. There are no rear view mirrors and it instead uses cameras and electronic displays. The rear wheels are close together to allow a streamlined body. The total aerodynamic drag is minimal because both the drag coefficient and frontal area are small (see drag equation). The drag coefficient (Cd) is 0.159, compared to 0.30 - 0.40 for typical cars. The external dimensions of the car are long, wide and tall. There is of storage space. The car features an aircraft-style canopy, flat wheel covers and an underbelly cover to smooth the airflow. The engine cooling vents open only as needed. For light weight, the car uses an unpainted carbon fibre skin over a magnesium-alloy subframe. Individual components have been designed to be low weight, including engine, transmission, suspension, wheels (carbon fibre), brakes (aluminium), hubs (titanium), bearings (ceramic), interior, and so on. Empty vehicle weight is . The body and frame are designed with crush/crumple zones and roll-over protection, and the tandem seating means large side crush zones. Volkswagen claims protection comparable to a GT racing car. The car has anti-lock brakes, airbags with pressure sensors, and stability control. The engine is a one-cylinder diesel producing just . It drives