261 MPG Volkswagen XL1 diesel plug-in hybrid to be produced in limited quantities

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credit: VW

Here you can see what the drivetrain is like. The diesel engine is a small 0.8-liter two-cylinder TDI (35 kW / 48 PS), the electric motor generates 20 kW, and they are mated to a 7-speed dual clutch transmission (DSG). The battery pack is lithium-ion and can hold 5.5 kWh. In electric mode, the TDI engine can be disengaged via the clutch and shut down.