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Petrol, diesel, hybrid, electric – which is best?

Petrol, diesel, hybrid, electric – which is best?

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 (CO2), 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.

Petrol and diesel models

The Toyota Aygo manages to be a cheap, fun and economical city car with a petrol engine that manages 62.8mpg and emits just 106g/km CO2

Most vehicles still have conventional petrol or diesel engines. But, the good news is that they are becoming increasingly fuel 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.

Diesel engines are more economical than petrol engines, especially for longer journeys, which means they also have lower CO2 emissions. The downside is that diesel engines can emit particulates that harm local air quality more than petrol engine emissions. The emissions are reduced if the vehicle has a diesel particulate filter (DPF).

Green models

BlueMotion is Volkswagen’s super-efficient range, the new UK-spec Polo BlueMotion can manage 83.1mpg and emits just 90g/km CO2

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 better aerodynamics, reduced weight, lower-resistance tyres, lower 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 you must work out if your mileage will give large enough savings to pay back the extra investment. At least one manufacturer is applying efficient technologies to all its vehicles.

Hybrid models

The latest Toyota Prius hybrid emits just 89g/km CO2 and can achieve 72.4mpg – amazing figures for a five seat hatchback

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 CO2 emissions. At higher speeds, the engine and the electric motor may work together to provide more power.

At the moment, only petrol-electric hybrids are available in the UK. Diesel hybrids are due soon. Although hybrid vehicles can offer lower emissions in towns and cities, they can still be driven for long distances thanks to the petrol engine. Hybrid cars are generally more expensive than comparable non-hybrid ones.

Plug-in hybrid vehicles will be here soon. You plug these into an electricity supply to recharge the electric motor’s battery, which means higher electric power capacity and therefore lower exhaust emissions.

Electric vehicles

The Mitsubishi i MiEV is an all-electric vehicle that’s excellent to drive, exists now, and is due to be available in the UK before the end of 2010

We are at the start of an electric revolution. There are currently only a few electric vehicles to buy today. This will change soon, as many manufacturers are planning to bring new electric vehicles to the marketplace.

Electric vehicles do not produce any emissions. If they are recharged using electricity from renewable sources, they are potentially the lowest emission vehicles you could use. The problems are the limited range before they need recharging and their relatively low top speeds. Nonetheless, they are ideal for short journeys in urban environments, where the number of recharging facilities is expanding.

Although you can buy electric cars, vans and scooters, the choice is limited. Electric cars with the latest technology can be expensive, but their running costs are very low.

Biofuels

Saab saw biofuels as having real potential and brought vehicles such as the 9-5 BioPower to market, but sufficient financial incentives for biofuels currently don’t exist in the UK

Some vehicles available in the UK can be powered by biofuels. Biofuels are renewable; they can be produced from plant material or waste vegetable oil, for example.

Some petrol engines can be adjusted to run on bioethanol or blends containing a high proportion of bioethanol. Bioethanol fuel is only available at a few fuel stations. Some diesel engines can run on biodiesel or biodiesel blends, but these fuels too have limited availability.

Check the sustainability credentials of all biofuels. The most sustainable are those made from waste or non- food crops. The biofuels currently being developed from sources such algae promise to be the most sustainable.

Gas

There aren’t many vehicles around that are powered by gas but this Volkswagen Caddy van is one of them, and it’s greener than most as it runs on biogas

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. CNG is used primarily for heavier commercial-type vehicles.

Biomethane is renewable bio-gas derived from sources such as landfill sites, so it’s very sustainable but unfortunately  is not widely available.

Hydrogen

Honda is the first manufacturer to produce a car powered by a hydrogen fuel cell,
the FCX Clarity,
which is currently on the road in America and Japan, albeit it in limited numbers


Hydrogen is 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. These challenges include the
lack of a hydrogen refuelling infrastructure, the expense of making
hydrogen-powered vehicles and producing hydrogen sustainably.

Summary

While some manufacturers are offering greener variants of some of their models, BMW has applied its EfficientDynamics technologies throughout its model range, with the aim of ensuring all of its cars are still great to drive while being class-leading in terms of low emissions

Zero-exhaust-emission vehicles are the ideal for urban areas. Electric vehicles achieve this. They are available, and the choice will increase with time.

If you need a longer range than an electric vehicle offers, a hybrid vehicle may be the answer, and it helps to reduce emissions from urban driving.

If electric or hybrid vehicles are impractical, choose a vehicle that has best-in-class efficiency. And if new vehicles are too expensive, remember, second-hand green vehicles are also available.