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Green car technologies explained


What are the latest green car technologies?

Petrol, diesel, hybrid, plug-in hybrid, electric, extended-range electric – which green car technology is best for you?

So you want an economical, low emission car , but with new technologies appearing all the time, do you choose petrol, diesel, hybrid, electric… or something else…?

Vehicles emit carbon dioxide (CO 2
), the major cause of climate change. They also produce other emissions that impact on the quality of local air (the air that we breathe). New cleaner green vehicles are coming onto the market all the time, so we can do our bit by choosing lower-emission vehicles. This also saves us money on running costs. But how do you know which technology to choose? This is a quick guide to help you decide what’s best for you.

New Petrol Engines

Most vehicles still have conventional petrol or diesel engines. Contrary to what you may read in the media, they won’t be dying out any time soon – instead they will continue to become more efficient. Better efficiency means fewer emissions. Petrol engines are generally favoured for smaller city-type cars, as they are lighter, more responsive for urban driving and cheaper to manufacture. There are new petrol engines, such as two- and three-cylinder units, coming on to the market which are extremely efficient.

Nissan Micra DIG-S
68.9 mpg, 95 g/km CO

The Nissan Micra DIG-S does 68.9 mpg with only 95 g/km CO2


Diesel Engine Efficiency

Diesel engines are more economical than petrol engines, which means they also have lower CO 2
emissions. If you mostly drive long distances, an efficient diesel engine may be your most economical option. The downside is that diesel engines can emit particulates that harm local air quality – more than petrol engines. The emissions are reduced if the vehicle has a diesel particulate filter (DPF), which all new diesel cars must now have to comply with Euro 5 regulations. However such extra technology to ensure that diesel engines are cleaner all adds to the additional cost of diesel engines.

BMW 520d EfficientDynamics Saloon
62.8 mpg, 119 g/km CO


Green Petrol and Diesel Models

Many car manufacturers offer green versions of their conventional models. These are more fuel-efficient and so have lower emissions. Certain common technologies are used to achieve such fuel savings. These include improved aerodynamics, reduced weight, lower-resistance tyres, longer gearing, remapped engine management systems, stop-start systems and less load on the engine from ancillary items. Green models often have a price premium. This means that you need to work out if your mileage will give large enough savings on fuel to pay back the extra investment. At least one manufacturer is applying efficient technologies to all its vehicles.

Volkswagen Polo BlueMotion
80.7 mpg, 91 g/km CO

The Volkswagen Polo BlueMotion does 80.7 mpg with only 91 g/km CO2 emissions

Hybrid Electric Vehicle (HEV)

A hybrid vehicle has a conventional engine and a battery-powered electric motor. The idea is that the engine is used most of the time, but in most hybrids the electric motor alone can provide power at low speeds. In urban use, this means a hybrid car should offer reduced fuel consumption and CO 2
emissions. At higher speeds, the engine and the electric motor may work together to provide more power. Over the last few years only petrol hybrids have been on sale in the UK, however diesel hybrids are now available. Although hybrid vehicles can offer lower emissions in towns and cities, they can still be driven for long distances thanks to the petrol or diesel engine. Hybrid cars are generally more expensive than comparable non-hybrid ones, because they effectively have two powertrains.

Peugeot 3008 HYbrid4
74.3 mpg, 99 g/km CO

The Peugeot 3008 HYbrid4 does 74.3 mpg with only 99 g/km CO2 emissions

Plug-in Hybrid Electric Vehicle (PHEV)

Plug-in hybrid vehicles will be here soon. These share similar technologies to hybrids but you can also plug these vehicles into an electricity supply to recharge the electric motor’s battery, which means higher electric power capacity, a longer driving range on the electric motor – possibly up to 20 miles or more – and therefore lower exhaust emissions. Both petrol and diesel plug-in hybrids are due to be launched over the next year or so.

Volvo V60 Plug-in Hybrid – First Drive
150 mpg, 49 g/km CO

The Volvo V60 Plug-in Hybrid - First Drive does 150 mpg= with only 49 g/km CO2 emissions

Electric Vehicle (EV)

We are at the start of an electric revolution. There are currently only a few electric vehicles to buy today but this will change soon, as many manufacturers are planning to bring new electric vehicles to the marketplace. Electric vehicles do not produce any ‘tailpipe’ emissions. If they are recharged using electricity from renewable sources, they are potentially the lowest emission vehicles you could use. Problems associated with electric cars are perceived to be their limited range, the need to regularly recharge them, and their high purchase cost. However, they are ideal for short journeys in urban environments, where the number of recharging facilities is also expanding. Although you can buy electric cars, vans and scooters, the choice is currently limited, but this will change over the coming years. Electric cars with the latest technology can be expensive to buy, but their running costs are very low, and they can benefit from incentives such as congestion charge exemption and zero company car tax.

Nissan LEAF
N/A mpg, 0 g/km CO
if recharged from renewable energy


Extended-Range Electric Vehicles (E-REV)

Extended-range electric vehicles are electric vehicles at all times, in other words the drive to their wheels is provided by an electric motor powered by a battery, which is normally recharged by plugging in to an electricity supply. However, unlike pure electric vehicles, they also have a range-extender generator on board – so if the battery charge runs out, then the generator starts up and recharges the battery, and continues to power the car. Extended-range generators are usually relatively small petrol engines and can provide up to an extra 300 miles of driving range in some cases – thereby getting round the ‘range anxiety’ associated with electric vehicles. Extended-range electric vehicles are even more expensive than pure electric vehicles because in addition to a large battery they also have a petrol engine. A range-extended electric vehicle may sound like a hybrid, but it’s actually the opposite – whereas a hybrid predominantly always runs on the petrol or diesel engine with some battery assistance, a range-extended electric vehicle is always electric, with back-up from a petrol engine.

Vauxhall Ampera
175 mpg, 40 g/km CO



Biofuels are produced from plant material or waste vegetable oil, so they are renewable. Most fuel in the UK today includes a small percentage of biofuel, but some vehicles can be powered by biofuel in higher quantities, up to 90 or 100% in some cases. Some petrol engines can be adjusted to run on bioethanol or blends containing a high proportion of bioethanol, such as E85, but bioethanol fuel is only available at a limited number of fuel stations. Some diesel engines can run on biodiesel or biodiesel blends, but these fuels also have limited availability, and can vary in quality. Biofuels were in favour with the UK government for a short time a few years ago. When certain biofuels were found to be damaging the environment, due to issues such as rain forests being cut down to grow biofuels, they fell out of favour. Since then much work has been done to ensure the sustainability credentials of biofuels and if they are produced sustainably – for example from waste or non-food crops – then biofuels do have the potential to be an important part of the overall transport fuels mix, providing a low carbon fuel when other technologies may not be suitable. Biofuels may result in lower emissions, as well as more power, but they do not necessarily result in improved fuel economy. Some mainstream manufacturers had cars on sale a few years ago that could run on biofuels, such new cars are now in very short supply in the UK due to lack of government financial incentives for manufacturers and the consumer.

Lotus Eco-Elise


Gas Powered Vehicles

Gas, such as liquefied petroleum gas (LPG) or compressed natural gas (CNG), can power some vehicles. Vehicles that can run on LPG are usually dual-fuel conversions, i.e., they also run on petrol. LPG is a slightly cleaner fuel than petrol, and it is certainly cheaper. LPG was promoted widely a few years ago, but with the recent emergence of other green car technologies it now has a much lower profile. CNG is used primarily for heavier commercial-type vehicles. Biomethane is renewable biogas derived from sources such as landfill sites, so it’s very sustainable – in fact it has one of the lowest carbon footprints of all transport fuels – but unfortunately it is not widely available. Although gas can have lower emissions and can be cheaper than petrol or diesel, it won’t necessarily deliver better miles per gallon.

Volkswagen Caddy EcoFuel Van


Hydrogen Fuel

Hydrogen is seen as the ultimate future fuel, as its only emission is water. Some manufacturers are either producing or trialling cars powered by hydrogen, but they must overcome some challenges before we can all drive around in hydrogen-powered vehicles, including the lack of a hydrogen refuelling infrastructure, the expense of making hydrogen-powered vehicles, and producing hydrogen sustainably.

Honda FCX Clarity


Summary of Technologies

Zero ‘tailpipe’ emission vehicles are ideal for urban areas. Electric vehicles achieve this. They are available today, and the choice will increase with time. If you need a longer range than a pure electric vehicle offers, a hybrid or an extended-range electric vehicle may be the answer, as both help to reduce emissions from urban driving, but don’t have the range limitations associated with a pure electric car. If you want an economical vehicle for long distances, then an efficient diesel may be the best bet. If you want a vehicle with a low purchase price and low running costs mainly for short journeys in and around the city, with occasional longer distance driving, then there are increasing amounts of highly efficient petrol cars. Whatever type of car you need, there will be class-leading models.

Find out the leading green city cars in our special
Green Car Guide