I concur with these findings and am just amazed it has taken the authorities all this time to come to this conclusion! I have owned and driven diesel powered cars since 1978 which is when I personally discovered their benefits.

Laurie Griffiths, Littlehampton, W.Sussex., UK

Will the Department of Transport have a word with Her Majesty's Revenue and Customs regarding company car tax if they are to recommend Diesel engined cars? Ever since company car tax was based on CO2 emissions they have loaded an extra 3% of taxable benefit on diesels even for the cleanest EU4 engines (which did not have the loading until this year). My company car (1.9 Diesel VW Passat) is recommended as a low emission family car and returns 50+ mpg but I still have to pay a penalty to HMRC in my income tax.

Phi, Wirral, UK

You can double the top rate of car tax to £600. Treble it, quadruple it, it won't make a lick of difference. If you're willing to pay £40,000 for a gas guzzling 4x4, then £1 a litre for all that gas it guzzles, you can probably afford £100 a month to keep it taxed. You would also, of ocurse, be doing your patriotic duty by helping to pay for more commissions to work out that we need to pay more tax.

Jonathan Trueman, Manchester, UK

First diesel was good, then it was bad, then good again, but the fuel (in UK) was more expensive than petrol. Authority has changed its story on the environmental merits of diesel-engined passenger cars more times than Jack Straw after the London bombings.

Andrew Milner, Yokohama , Kanagawa

The article says

" The campaign’s underlying message is that a diesel car is the best option ... A diesel car will typically travel at least 20 per cent farther for the same amount of fuel as a similar-sized petrol car"

I can't find this stated on the D(a?)fT website, which opts for petrol for urban drivers. I wonder if the Times writer Ben Webster can tell us if "amount" means volume or mass. I suspect volume, but mass is the more sensible comparator. The mass energy density of petrol is slightly HIGHER than that of diesel !!

But let's not let mere facts interfere with the orthodoxy.

Also, when comparing petrol/diesel engines are they using like for like performance, or accelerating slower with the diesel?

Stephen Phillips, London, UK

whatever the bandwagon governments of the world believe concerning global warming and the contribution traffic has on it they must realise that cars (ie private transport) are here to stay and must be managed intellegently. Preventing the majority of the workforce the ability to use private transport will result in a return to primative economies of the middle ages...........the solution is to get away from oil based fuels (for many reasons) without substituting them wholly for fuels based on crops which will just end up in large parts of arable land and untouched countryside being turned over to its production. So far the only feasible fuel alternative on the horizon is hydrgen fuel cells but we must keep searching for more alternatives.

Its a pity the lean burn engine wasn't given the development afforded to other systems, maybe we wouldn't have this problem on such a scale if it was.

jack, cardiff, uk

There is pleny of Diesel around!
The main fact is that oil companies make a few pennies on every gallon/litre they sell. If consumption falls by 30% their profits fall by the same amount.
The original refining plant had to be designed to produce more petrol/benzine because that was in demand. So much so that the energy used was more to obtain more of the saleable product.
The diesel was then mixed with paraffin to give Home heating oil with the correct viscocity for use with the rudimentary burners. Modern oil burners in houses could use anything that could be made to flow. There are plenty of places in this country and in the world that are using oil and that other valuable resource LPG which have a better use than just warming buildings.
I know of no circumstances when these valuable natural resources are used to generate electricity and heat at the same time (CHP) in the domestic environment, in order to obtain an even greater reduction in emissions.

M Sheridan, Oldham, UK

Is the commentator who has chosen not to have kids as the answer to global warming really "alive"?
If the answer to the end of human civilization (and considerable else too) is the end of human reproduction...then the baby is truly out with the flooded bathwater!
This is ludicrous; we cannot save nature by denying it. We have to adapt and we have to modify our behaviour; we have to embrace new technology.
We are supposed to be saving the planet for our grandchildren...they won't thank us for opting for barrenness. Crazy.
As for cars...of course, you have to do the right thing in the context of your own life. The wrong thing will always be buying a brand new petrol guzzling 4x4 every three years; the better thing would be to buy more efficient car, and replace it less often. A simple choice like that, replicated millions of times, makes a considerable difference. Don't belittle any gram saved.

John Pownall, Bridport, Dorset

How on earth can one believe that hydrogen will be "the usual fuel of choice" in 2015 ? By the way hydrogen is just like electricity: it doen't grow on trees.

Demassieu, Paris,

Why not just stop encouraging people to own cars in towns and cities where there is a public transport alternative by not providing 'residents only parking'. We all pay (or should pay) VED for the right to use the road, why should residents be given the right to 'own' the road outside there house?

We should adopt the Japanese system where no-one is allowed to own a car unless they can first prove that they have somewhere off street to keep it near their home. Less cars leads to less congestion and less pollution. But also, less money for the government, who don't really want us to own less cars or drive them less. However, it sounds good for them to say they want to reduce pollution so they can increase motoring taxes and make us feel that it is justified.

Frank, Winchester,

No point in knocking diesel cars for emissions; apart from private cars and motorcycles, just about every other form of motorised transport, air, land or sea, runs on oil fuel. Oil fuel has been with us for a very long time, and until a viable alternative becomes available, it will stay. Diesel engines are considerably more fuel efficient than their petrol equivalents.

A. Taylor, Nottingham,

Is there really anyone left who still buys into the hybrid story? These cars have the biggest "carbon footprint" of all, because it takes two (CO2 belching) factories to make them, one for each motor. In fact, the vast majority of lifetime CO2 emissions for any car comes before it's even been driven out of the factory. The "greenest" car to drive is anything built a long time ago and bought second hand, because it's currently neither being built in a factory nor rotting in a landfill site. CO2/km measurements are an irrelevance invented by car manufacturers to persuade people to keep buying new cars, instead of doing the eco-friendly thing and holding on to their old ones.

Johnny, London,

Of course a Diesel is more likely to give pedestrians cancer due to the particulates and harmful emmissions generated when compared with a petrol engined vehicle.

The best way to reduce vehicular emissions is to not buy a new car therefore saving all the C02 that would have been generated in production. Classic sports cars cherished, last decades and are therefore the most environmentally friendly car available.

The best overall way of course is to turn your central heating off as this is responsible for more emissions than your car will ever make. Either that or don't have children (my choice) thereby saving generations of C02 emissions in one simple decision.

Motorists selfish? I don't think so, parents are more so.

Alastair, Leamington Spa, UK

I do like things being recycled. It can't be more than fifteen years when the diesel was seen as the economic engine, only to be slated in subsequent years by the enlightened "green" lobby as dirty and pure evil. The Govt of the day even reduced tax incentives to steer people AWAY from diesel power units.

How society advances!

cynic sid, Norway,

"Nigel Underdown, the trust’s head of transport, said that there would be a greater environmental benefit from doubling the top rate of road tax "

Why always try to price people off the road, all that achieves is making us less likely to be able to afford the latest most efficient cars. Why not make more environmentally friendly options so cheap we'd be stupid not to opt for them.

Paul, Isle of Wight, UK

Following on from this, I think people should be encouraged to use grease. Earlier this year we took part in a grease challenge and drove from Washington DC to Costa Rica in an old mercedes '74 diesel. We spent a total of £60 on diesel and the rest was waste grease from restaurants (for free). So if you really want to make a difference, why not fill up with grease. Our carbon emission was zero for 80% of our 7,500 mile journey. www.greaseballchallenge.com

Nicola Matsukis, London, London

“The most effective way of capping or reducing fuel consumption would appear to be to increase the cost of buying and running standard cars" - anyone ever thought of building houses and shops close to where people work?

Jimd, Norwich, UK

I have just had my Ford Dayvan fitted with LPG as a family of six . I have done my bit but it is not easy to find LPG in the UK . But in Europe is a lot lot better.

Paul, Mazenzele, Belgium

In Spain, as in may countries, driving without the aircon on is dangerous in summer due to the high ambient heat. Our car at present, a 48 mpg (5,8 litre/100 km) Ford Focus (average over 6 years) has a temperature of about 50 Deg C when we get in after it has been parked in the sun. I could never reason (except for greed) why the UK charges higher taxes for diesel when it is greener especially when our previous Toyota Corolla 1600 cc petrol car averaged nearly 10 litres/100 km or 30 mpg over 220.000 km, which means that the Focus has saved 42% in actual liquid fuel quantity over it six year life so far even though it has a bigger and more powerful engine. As Don from the Lone Star State writes, the reduction in duty for diesel would in a very few short years put the government way ahead on its promise to reduce carbon emissions and the car industry will come up with anti-pollution devices for diesel cars until hydrogen is the usual fuel of choice in about 2015.

B J Deller, Marbella, Spain

Cars are expensive enough to run at the moment, and there are no realistic alternatives, especially in more rural areas.
Private car use does not contribute significantly to the UK's CO2 emissions, which hardly contributes at all to global CO2 emissions.
They are however essential for modern life, and I for one quite like them.

Sam Oxley, Cheshire,

So, let's see if those redoubtable British Boffins can't come up with a cost effective algae farm that will produce enough bio-diesel to make up the difference. A 20% reduction in crude oil consumption is nothing to sneeze at.

Don, Houston, Texas, USA