Most manufacturersare now obliged to report figures now for CO2 as well as MPG. Its pretty obvious thatthe more fuel you burn for any given distance, the higher the CO2 and the lower the mpg. What most people don’t realise is that there is an exact formula exactly linking the two figures.

It’s far more accurate to measure how much CO2 your car produces using the MPG, because manufacturer figures are always very unreliable. For example a vicar who bought a car rated at 40mpg and does lots of long journeys at 50 mph is likely to get 50+ mpg, whereas a boy racer who spends most of his time with the front wheels spinning is closer to 30 mpg:

  • 30mpg is equivalent to 218g/km (Petrol) & 252 g/km (Diesel)
  • 40mpg is equivalent to 163g/km (Petrol) & 189 g/km (Diesel)
  • 50mpg is equivalent to 130g/km (Petrol) & 151 g/km (Diesel)

But hang on – doesn’t this mean Diesel is less environmentally friendly than petrol? Surely that can’t be true?

Well it is and it isn’t. Every litre of Petrol you burn creates 2.31 kg of CO2, whereas every litre of Diesel produces 2.68kg. However diesel cars tend to be more efficient (because they can run a higher compression ratio mostly) and this offset’s the difference because less fuel is burnt in the first place.

So there you go. And to make it a little bit easier, below is a handy graph which allows you to translate easily between mpg and co2 for any vehicle.

MPG to CO2

MPG to CO2

As a final note, I should point out that for a car to be able to compete with the train as a clean form of transport, it would have to do about 109mpg (~60g/km). Now that is a challenge!

Source: VCA data / Clear analysis


Not a question most of us have asked directly, but when you hear about Toyota Prius this and Lexus hybrid that, do you ever wonder what is the highest producing car on sale in the UK today?

Let me introduce you to the hall of fame, and you won’t be surprised to hear that it is exclusively populated by Italian supercars.

July 2000 – April 2002 – The most inefficient car in the UK was the one and only LAMBORGHINI Diablo, producing a colossal 590g/km of CO2. That’s almost a bag of sugar’s worth of CO2 every mile!

May 2002 – April 2005 – Ferrari were obviously not content to be left in Lamborghini’s wake, and up-ed their game, topping the table with the 456M GTA 2+2, a classic 4 seater producing 570g/km. (However if you did have 4 people that’s only 143 g/km each which is about the same as one person in a Ford Focus!)

May 2005 – September 2005 – Ferrari really show Lamborghini who’s boss with another entry, the mighty Enzo. You had to be invited to buy one by Ferrari, and they were a cool $1m a pop. And at 545g/km surprisingly less than a 456.

October 2005– August 2008 – As the Enzo ceased production it gave Lamborghini a chance to get back in the game with the Murcielago producing a positively respectable 500g/km. And you also may have noticed that over the last 8 years the supercars have (dare I say it) become cleaner? Lamborghini’s top of the range model has gone from 590 to 500 g/km. Have supercars gone all soft and reached for a pair of lentil sandals? Not a chance. In October 2005 Bugatti released the 250mph Veyron and all was right with the world again. Averaging a 596 g/km, at top speed this behemoth will gobble almost 2 gallons of fuel a minute. Doing some shopping? Well through town the Bugatti will officially produce 960 g/km of CO2. To put that in context it is the same as driving 9 and a half VW Polo Bluemotions at the same time. Short of towing a bonfire down the road behind a tractor with a hole in its fuel tank, its pretty hard to produce more CO2 / km than that. 

Of course there are a lot of other factors here, such as NOX levels, particulates, energy required to produce the vehicle, shipping, all the nasty chemicals produced in manufacture and so on, but that would all make this a bit dull.

So the “take-away message” is simple. If you really don’t believe in or care about global warming (and have a bottomless wallet), a Bugatti is the car for you!

The fastest and least efficient car in the world

The fastest and least efficient car in the world



Source: VCA data /