MPG is the new MPH

MPG is the new MPH: How far will your next car go?

By Simon Lewis

People once bragged about how fast their car could go; now it’s all about miles per gallon

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The Porsche 918 Spyder will hit 60mph in under three seconds, should be capable of 201mph and will be twice as fuel-efficient as a Mini Cooper

Next year’s Porsche 918 Spyder will produce 760 horsepower, hit 60mph in under three seconds and should be capable of 201mph.

But for once, those are not the headline figures. Thanks to electric motors on each axle (in addition to a 4.6-litre V8), by some reckonings the Spyder will be twice as fuel-efficient as a Mini Cooper.

And it’s not the only frugal supercar. Ferrari’s replacement for its fl agship Enzo is said to be a hybrid, and McLaren’s forthcoming P12 will have a KERS energy-storage system to save fuel.

Why have the makers of the world’s most powerful cars started caring about fuel efficiency?

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35 MPG: THE PAST: Ten years ago the UK’s top-selling car was the Mark 1 Ford Focus and 35mpg was perfectly good when petrol was 70p per litre. A bioethanol version was offered in some markets: an eco-friendly strategy that’s since gone out of fashion

Simply, because we have. People used to brag about their cars’ top speed.

Now that the cheapest hatchback can easily exceed the legal speed limit, and since petrol prices spiked to £1.42 a litre in April, the new question is: how far can you go on a gallon?

The seven cars here, all out in the next six months, can make a gallon of petrol stretch twice as far as the average car of ten years ago. They have to.

The EU demands ever-decreasing average CO2 emissions and cars that burn less fuel emit less CO2. Most car makers have already hit the 2015 target.

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67 MPG: Skoda Rapid 1.6 TDI DPF 90; £13,000 approx; Out November

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70 MPG: Honda Civic 1.6D; Price TBA; Out early 2013

Some hybrids are efficient enough for the 2020 target. How are they doing it?

One way is hybrid technology – where electric motors capture and reuse energy that would otherwise be lost while braking. But it adds a great deal of cost.

A small but significant amount of fuel can be saved using Stop/Start engine technology – where the engine cuts out when you’re idling at the lights and cuts back in seamlessly, thanks to powerful new starter motors. 

A third method is valve timing: for greater efficiency the cylinder valves open at different times, and for different durations, depending on the speed of the engine.

You can even deactivate whole cylinders if not needed: the new Bentley V8 is actually a V4 some of the time. There’s stratified fuel injection, where the fuel is sprayed into the cylinder at exactly the right time and place for maximum efficiency.mpg 5

73 MPG: Audi A3 1.6 TDI; £20,155; Out October

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74 MPG: Mercedes A180 CDI BlueEffciency; £21,000; Out November

And there’s turbo- and supercharging, which allow more compressed air/fuel to be injected into the cylinders, allowing the use of smaller, more efficient engines without sacrificing performance.

Use all of the above – plus lighter materials, better streamlining, better tyres, higher-voltage batteries and longer gears – and you can get nearly twice the miles from a gallon of petrol than you could without them. And the technology is constantly improving.

That’s why the latest cars can use small three-cylinder (Ford, Peugeot/Citroën, VW) or even two-cylinder (Fiat, Alfa Romeo) engines without feeling underpowered. Britain is leading the way in all this.

Ford’s Dagenham plant, supplying half of all Ford diesel engines, now makes a 1.6 EcoNetic that can get 85mpg – ensuring £1.5 billion of investment over five years.

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79 MPG: Volvo V40 D2 28; £19,745; Out this month

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88 MPG: Renault Clio 1.5 dCi 90; £14,000; Out September

BMW will build its three-cylinder engines for hybrid cars near Birmingham. Jaguar Land Rover is creating 1,100 jobs in the UK with an emphasis on green R&D.

And the batteries for Nissan’s electric LEAF will be made at its Sunderland plant.

The only fly in the ointment is: can the official mpg figures for these new cars be achieved in real life?

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134 MPG: Toyota Prius Plug-in; £27,895; Out this month

The European test procedure simulates the stop-start, fuel-intensive conditions of city driving (the ‘Urban’ figure), then the smoother conditions of motorway driving (the ‘Extra-Urban’ figure) and then averages them into a Combined figure.

For ease, like most other publications we use the Combined figure.

But in practice you have to be a very, very conscientious driver to meet it.

You may have to use some hypermiling techniques.

But even if you assume as many do that real-world mpg is about two thirds of official mpg, this is still a remarkable time for car engineering.

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313 MPG: THE FUTURE: By 2014, Volkswagen will put this XL1 concept into limited production. It’s a plug-in hybrid combining a 47hp, 800cc two-cylinder diesel with a 26hp electric motor and ultra-light, ultra-aerodynamic construction. It will only do 99mph, but VW promises an incredible 313mpg



80mph is 15 per cent less fuel-efficient than 70mph.


And anything else that spoils your aerodynamics


It will stop you over-using the brake/throttle.


Braking wastes fuel.


Squashy tyres waste forward energy


Shift up sooner to be in a higher gear, with lower RPMs.


Easier said than done…


Air conditioning burns fuel.


Or at least more gently.

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