Car buyers guide: You, your car and the environment

Line of vehicles

Forget most of what you’ve heard about hybrid, electric, or biodiesel – there is no such thing as a ‘green’ car. All cars damage the environment; it’s just that some do more damage than others.

The greenest car is the one left at home in favour of cycling to work or walking to the shops, but assuming you need to own a car, how can you limit your impact?

Car buyers guide

The following guide provides tips on how to make your driving greener and safer as well as the relative merits of different types of car.

New vs second-hand cars

Going for a second-hand car can be a green as well as financially-canny alternative buying new.

Cars lose up to half their value after three years, but at that age should still look and drive like new and remain reliable. New cars tend to be more reliable than second-hand cars, but their assembly, delivery and even marketing have consumed significant resources before you have driven them off the dealer’s forecourt. Breakdown cover for secondhand cars costs from less than £40.

It’s best to choose with a well-documented service history. It can make economic sense to spend more repairing a vehicle than its market value. Reliability is the key. Once a vehicle becomes unreliable sell it. You can protect yourself against unexpected repair bills by buying a car warranty.

Buy small, hire large

Buy as small as you can for your day-to-day needs. You may decide you need a big car because you have relatives that live over 400 miles away. If you only visit them twice a year, however, and most of your driving is done in a 50-mile radius a big car may be inefficient. By buying a smaller car for the majority of driving, and renting a bigger car for the long trips, you will save money.

Car sharing

Car clubs offer money-saving and green alternative to private car ownership, and some people simply have an informal arrangement with friends or neighbours,. If you drive less than 6,000 miles per year, it is claimed a car club could save you up to £3,500 a year. Many people don’t notice the true costs of running a car, but when you add up the cost of tax, MOT, fuel, servicing, repairs, depreciation and parking it is often more than you expect.

Fuel Consumption

A car with better fuel consumption will contribute less to global warming. This is because the more fuel you use, the greater the CO2 emissions. CO2 is the main greenhouse gas and private road transport produces 85% of transport-derived greenhouse gas. Another incentive is that vehicle excise duty (VED or car tax) is based on the level of

CO2 emissions, therefore less polluting cars pay less road tax.

Engine size

In general, the larger and/or more powerful the engine, the more environmentally unfriendly it is.

Corporate social responsibility

Car makers in Europe as subject to ever more rigorous regulation. Invariably, these measures are fought by the car lobby, but you can send a powerful message by asking dealers questions about the environmental performance of the car and its manufacturer. If the dealer does not have published material about it, or offers you one which does not answer your questions, you should ask the sales person directly. By asking precise questions about the environmental practise and standards of the manufacturer, you will be demonstrating that you are concerned about the impact your purchase will have on the environment. You are sending out the message that the environment is a crucial factor in your choice of car. That message will help to promote environmental thinking in the motor industry.

Exhaust emissions

Cars emit a complex chemical cocktail of exhaust gases. While technology such as the catalytic converter is slowly bringing us cleaner cars, predicted traffic growth will negate these benefits. Here we list the major pollutants and the damage they are causing to our bodies and planet:

Carbon dioxide

Although CO2 is not a health-damaging gas, it is the main cause of climate change and arguably the single biggest pollution threat that humankind faces today. Each of us is responsible for producing on average 12 tons of

CO2 each year and approximately one third of that is produced from driving (the actual figure depends on the type of car you use and how much you drive). Road transport is the fastest growing source of CO2 and accounts for around one quarter of Britain’s emissions. Burning one litre of petrol produces around 2.5kg of CO2. In other words, the average car produces twice its own weight of CO2 per year. The only way to cut our emissions is to cut our use of fuel, by using more fuel-efficient vehicles and driving less.

Carbon monoxide (CO)

At high concentrations, carbon monoxide gas kills by impairing the oxygen carrying capacity of the blood. Lesser concentrations can affect the central nervous system and the heart, and cause shortness of breath. CO also adds to ground level ozone, combining with other pollutants to form photochemical smog; and is one of the minor anthropogenic gases causing climate change. Road vehicles are responsible for no less than 85% of Britain’s CO emissions.


This is unburnt fuel, which is a proven carcinogen. HC’s react with various oxides of nitrogen to form ground level ozone and photochemical smog leading to respiratory problems in humans and damage to plant life. HC’s also contribute to global warming.

Nitrogen oxides

NOx are the pollutants most strongly linked with acid rain, combining with water vapour to form a dilute but deadly nitric acid solution, causing serious damage and inhibiting the growth of plants. NOx are also contributing pollutants to photochemical smog, they irritate the lungs, and increase susceptibility to viral infections.

Sulphur dioxide

Petrol and diesel engines emit small quantities of sulphur dioxide which, in high concentrations, can cause breathing problems, affect plant growth, contribute to acid rain, and damage buildings.


Diesel engines emit particulates (or soot) which is linked with asthma. This especially affects children as they use their lungs more than adults, their lungs are more susceptible and they are closer to the source of the exhaust. If you buy a diesel, ensure it is fitted with a diesel particulate filter (DPF). If you buy new, seek out a car that meets the Euro6 environmental rating.

Petrol or diesel?

Neither engine type is truly green or sustainable – not least because oil reserves are essentially a finite non-renewable resource. There is a popular belief that due to their lower average

CO2 emissions, diesels are better for the planet. Diesel engines are generally more efficient at burning fuel and using the created power, they also warm up in half the distance of their petrol counterparts (the most critical period for vehicle emissions). As such they produce less carbon dioxide (CO2), carbon monoxide (CO) and hydrocarbons (HC) than the equivalent petrol engine. Unfortunately it appears that it is people, particularly those in built-up areas, that may be paying the price. It is believed that 4,000 deaths are caused by air pollution in Britain every year, with people with respiratory problems most at risk.

Diesels emit the bulk of emissions that endanger health, causing asthma, chronic bronchitis, heart disease and cancer, and such vehicles will from 2020 have to meet the strict Euro 6 emissions rating. Most diesel cars have yet to meet Euro 6.

Car makers can now offer as an option a filter for diesel-engined cars that completely removes all trace of particulates form the exhaust. If most of your driving is in urban areas, ensure the car you buy meets the Euro 6 environmental rating.

Alternative fuels

Both central government and local authorities are becoming increasingly aware of the impact of transport on the environment and, consequently, are seeking to promote various solutions. A succession of fiscal changes over recent years which affect the rates of excise duty on vehicle fuels, have improved the financial attractiveness of these alternative fuels.

Natural Gas

Quieter, cleaner and cheaper. So why aren’t more cars running on these fuels? Availability remains a problem, although recognition by manufacturers into the potential of gas power, and the introduction of cars that can run both on petrol and gas (hybrids) has prompted significant development in this area. Petrol and diesel engines can both be converted to run on Compressed Natural Gas (CNG) and Liquefied Petroleum Gas (LPG).

Compressed Natural Gas (CNG)

CNG is a highly compressed form of methane. Natural gas vehicles operate quietly and waste less fuel when at a standstill. They emit up to 30% less CO2 and 70% less CO; emissions of sulphur and particulates are almost zero. It is the cleaner of the gaseous fuels and a popular choice for municipal vehicles. However, there are few public access refuelling sites in Britain.

Liquefied Petroleum Gas (LPG)

LPG consists of 90% methane, produced during petroleum refining. Emissions are generally lower than from diesel and petrol engines and LPG causes less wear and tear to engine and exhaust systems. LPG vehicles are less powerful than their petrol driven counterparts though this should not be an overriding concern for the green car-driver. They have some disadvantages, though, such as cold start problems and valve-seat wear. But LPG has an important role to play as a cheap (half the price of lead-free petrol), green alternative in the short/medium term.


Electric vehicles are efficient, produce low noise and zero emissions in use; characteristics well suited to urban environments. Apart from the technological problem with the weight and capacity of the battery, the major environmental variable is the method used for electricity generation. There are obvious environmental advantages if the source of power is renewable and ultimately sustainable such as solar, wind, tidal or hydroelectric. The latest electric cars such as the Nisan Leaf and in particular the BMW i3 offer excellent performance.

Ethanol and methanol

Ethanol is a product of grain alcohol distilled from sugar cane and rapeseed oil. The growing crops consume as much CO2 during the photosynthesis process as it releases during combustion so there is no global warming effect. Conventional internal combustion engines can run on ethanol or methanol with minor modifications. However, Europe and Japan do not have the land space available to grow the vast crop that would be needed to fuel all vehicles. The use of fertilisers would also generate additional environmental problems. Furthermore, ethanol and methanol both have a lower energy density than petrol, so larger fuel tanks are required.

Fuel cell

A fuel cell operates like a battery, but unlike batteries, fuel cells are almost endlessly rechargeable. Emissions are much smaller than from the cleanest of fuel combustion processes due to their reliance on a chemical reaction rather than combustion. The main waste product is water and in natural gas-fuelled cells a little carbon dioxide too. The cells run on hydrogen, which reacts with the oxygen from the air in such a way that a voltage is generated between two electrodes, and the reactions occur in a chemical mediator known as an electrolyte. Some designs may consume hydrogen directly while others start with natural gas that is converted to hydrogen before entering the cell. If a fuel cell includes a ‘fuel reformer’ it can utilise the hydrogen from any hydrocarbon fuel, from natural gas to methanol and even gasoline. Major manufacturers such as Honda continue to develop fuel cell vehicles.

Hybrid vehicles

Hybrid vehicles combine an internal combustion engine with an electric motor and battery. Currently, hybrid electric vehicles are offering major progress in electric propulsion because they offer the advantages of electricity without the disadvantages of big batteries. Some use their engine to generate electricity for charging batteries to run an electric motor, while others use the engine and motor alternately depending on driving conditions. The advantages include increased fuel efficiency (up to 90% less pollution than ordinary cars), greatly reduced emissions (up to 50% less output of carbon dioxide), regenerative braking capacity which helps minimise the energy lost when driving, and the use of alternative fuels rather than being dependent on fossil fuels.

Hydrogen gas

A gas, but not a naturally occurring one. It is produced from other substances, for instance through the electrolysis of water, and can be stored in a variety of ways, the most common of which is storage in liquid form. The conventional internal combustion engine can accommodate hydrogen as a fuel source with only minor modifications. Exhaust emissions are very low, and the main product of combustion is water. The choice of power source used to initially electrolyse the water has environmental implications in its own right. Other drawbacks include the technical difficulties of on board storage and the high cost of production and distribution. When used in the combustion engine, hydrogen has the potential in the long term for substantially reducing emissions in the transport sector, though by how much depends on the material used and the production method. At present it is one of the most expensive substitutes for petrol and diesel, though if price were to reflect true environmental cost, hydrogen would become relatively better value. Research into the use of hydrogen in fuel cell powered vehicles continues.

Solar Power

Solar-powered vehicles are small, light, and silent. They are true ZEVs (zero emission vehicles) polluting neither on the street nor at the power station. However, solar power does not require direct sunshine but has the significant disadvantage of only being available in daylight. Battery design improvements should allow power from the solar cells to be ‘banked’ for use during hours of darkness. For the time being however, solar technology is too expensive for the market to bear, though prices are expected to fall as methods of mass-production are developed.

Compressed air

It is possible to run a car on compressed air, although it is best suited to powering lightweight quadricycles. Peugeot has revealed a hybrid car that is powered by a petrol engine when cruising and compressed air while in town. It is claimed the system offers fuel savings of up to 45% while driving in town. The new technology offers an interesting alternative to hybrid electric cars as it delivers zero tailpipe emissions in town but with none of the environmental impact associated with the production and disposal of batteries.

Safe driving

Technological advances mean that modern cars, with ABS, crumple zones, multiple air bags, all-wheel drive and side impact bars are seen as the safest in history. For those outside the car however, conditions are becoming more dangerous. From the perspective of the vulnerable road user, the cyclist and pedestrian, cars have become more aggressive and lethal, fitted with over-powered engines.

The ETA has had a long-standing interest in the promotion of both safer driving and safer cars, from the perspective of all road users. Campaigns such as the Safer Car Campaign, launched as long ago as 1994, aimed to highlight the need for a review of both car’s and driver’s capabilities. And our Car Buyers Guide was an early reference point for environmentally conscious motorists.

The advent of driverless cars promises ‘crash-proof’ vehicles unable to exceed local speed restrictions, but until then motorists have a moral as well as legal responsibility to drive beneath the limit.

Greener driving

There are ways that we, as drivers, can reduce our impact.

  • Join the ETA – when you buy breakdown cover from the ETA, you receive award-winning level of service while supporting an organisation that is entirely carbon neutral and in support of sustainable transport.
  • Drive less – Consider whether your journey is really necessary. Try to avoid using your car for short journeys, instead consider walking, cycling or using public transport.
  • Car share – share with a friend, colleague, neighbour or relative; set-up your own car pool or contact the National Car Share scheme
  • Careful car maintenance – regular servicing to ensure that your car is not producing above the legal level of emissions set by the government. This is worth bearing in mind if you buy a used car; a car with a good servicing record is likely to have lower emissions than a car with a poor record. A well-tuned car will run more efficiently and maintaining tyre pressure helps reduce fuel consumption.
  • Check your fuel consumption – it will help you get the most from your car, changes in overall fuel consumption may indicate a fault.
  • Lower your speeds – Keeping below 60mph reduces emissions, saves fuel (up to 30%) and makes you a safer driver.
  • Drive smoothly and save fuel – learn to anticipate the actions of other road users. Consider an Advanced Driving course by contacting the Institute of Advanced Motorists.
  • Switch off when stationary for more than 60 seconds; do not remain stationary while warming the engine.

Car buyers guide: Five reasons your next car might be greener

  1. Petrol prices. Petrol prices have an obvious if not immediate effect on buying trends.
  2. Fashion. Much has been written about the faltering popularity of 4×4 cars in urban areas, but whilst there is increased awareness about this type of vehicle having high emissions and posing more of a risk to pedestrians in the event of a collision, the move towards smaller cars by city drivers has as much to do with the passing of a fad as it does environmental enlightenment. The Mini, Fiat 500 and the Citroen DS3 are stimulating demanding for stylish, fuel efficient and lightweight city cars; vehicles that in general also happen to be kinder on the environment.
  3. Variable VED rates. Cars that use the most fuel and therefore emit higher levels of CO2 are now charged over £400 more VED (road tax) than the cleanest vehicles, a difference that will have an effect on buying trends, particularly on the secondhand car market.
  4. Environmental awareness. Climate change is one of the greatest environmental threats facing the world today. The carbon dioxide (CO2) found in the exhaust gas produced by petrol and diesel engines is not directly harmful to human health, but is the most significant of the greenhouse gases contributing to Climate Change. There is an increasing realisation that choosing a fuel efficient car can help reduce the amount of CO2 emissions for which we are responsible as individuals.
  5. Technology (DPF, hybrids, electric). Increasingly tough emissions targets for car manufacturers are encouraging advances in green technology. The advent of diesel particulate filters (DPF) such as those fitted to some of the category winners heralds a dramatic improvement in the environmental rating of diesels. DPFs remove the soot in the diesel exhaust gases that is so detrimental to human health. Hybrid cars are increasingly available and will soon be joined by mass-produced pure electric cars such as the Nissan Leaf.