Volkswagen will be debuting its 250 MPG (~ 106 km per liter) Twin Up! diesel hybrid later this month at the LA Auto Show. The Twin Up! uses a modified version of the XL1′s 47 hp, 800 cc diesel engine and electric hybrid drivetrain to return a claimed fuel consumption of more than 256 MPG and CO2 emissions of just 27 g/km on the European cycles.
Just a comparison. Toyota Prius yields about 50 MPG and generates about 100 g/km of CO2 emission. So Twin Up! is 5 times more fuel efficient and 4 times less emission than Prius.
The new Volkswagen diesel hybrid would, if sold in the US, carry the highest EPA mileage rating of any hybrid car.