Audi shows an A4 TDI concept e said to consume only 3.99 litres per 100km (58.95 US MPG) from the 88kW 2.0 TDI engine. Emissions are ultra low too.

A whole lot of motor industry effort is being directed towards greater fuel efficiency. Audi’s latest foray into the realm of fossil-fuel-saving is the A4 TDI concept e which uses Audi’s 2.0 TDI engine to produce 88kW (120hp) and 290Nm of torque, which really isn’t the story as far as fuel-saving is it? No, that story is its mileage, which happens to be 58.95 US mpg or just 3.99 l/km. CO2 output is said to be 105 g/km for this close-to-production concept.

These figures are quite interesting given that a concept vehicle like the Chevrolet Volt is aimed to last just over 40 miles before a recharge, which is the distance that General Motors estimates is what the average American travels between work and home.

A number of paths have been taken to ensure this type of fuel efficiency, like tyres optimised for road resistance, an economy training programme that can be accessed by the driver, brake power recuperation system that recovers power when braking and coasting to a stop and stores it in a battery temporarily. There’s the start-stop system that stops the engine running when the car stops. It’s a multi-pronged approach that will keep the car going for much longer than it usually would. We can’t help wonder though, if the fuel-efficiency curve is starting to flatten out a bit. How much else can be done to improve fuel and what is the next major breakthrough technology in this regard?

Gallery: Audi A4 TDI Concept e Consumes 3.99 liters/100 km (58.95 US MPG)