What is LPG?

The Queen is a fan. So are Tony Blair and around 117,000 British motorists. The object of their admiration? Liquefied petroleum gas (LPG), an environmentally friendly fuel. Her Majesty puts it in several cars in her fleet, while the prime minister has a couple of official vehicles that run on the ‘green’ gas.

Petrol station owners love LPG too, because it’s more profitable than petrol and diesel, even though it’s sold at about half the price of either (thanks to its low fuel duty). That means motorists can share the joy by making savings of up to 40% when they fill up with LPG, according to the campaigning group Boost LPG (http://www.boostlpg.co.uk).

LPG is a natural hydrocarbon fuel made up of propane and butane, and is an abundant by-product of the oil and gas industries. The burning of LPG produces less carbon dioxide than other fuels, meaning a smaller contribution to global warming.

It also has the property of turning from gas to liquid at atmospheric temperature if moderately compressed, meaning it can be easily stored as a liquid and turned back into gas simply by relieving the pressure. And because it is 250 times denser as a liquid, a lot can be stored in a relatively small container.

LPG has a lot of uses, including home heating, refrigeration, air-conditioning and the industrial manufacture of paper, textiles, glass and heavy ceramics. But it is in motoring where the gas is gaining most attention, with around 1,300 UK service stations currently offering LPG, which is sometimes known as Autogas.

Around 9million cars worldwide are run on LPG, about 117,000 of them being in the UK, where the Government supports LPG’s use by maintaining a low duty on the fuel and providing grants towards the conversion of some cars to run on LPG. For more information and to apply for a conversion grant, visit the Energy Saving Trust (http://www.est.org.uk).

Most major motor manufacturers – from Ford (http://www.ford.com) to Volvo (http://www.volvo.com) - produce vehicles that run on LPG as well as standard fuel. Cars that are fuelled by petrol can be converted to run on LPG too for about £1,700. Converting diesel vehicles is more costly because more work has to be done on the engine to make it compatible for both fuels.

About 200 companies in the UK are participants in the LPGA Approved Installer Scheme, which was set up in conjunction with the Department for Transport (http://www.dft.gov.uk). Motorists often shy away from converting because they find it hard to locate someone to do the job, but a comprehensive list of approved installers can be found on the LP Gas Association’s website (http://www.lpga.co.uk).

The advantages of LPG-powered cars are a more environmentally friendly ride that’s also quieter with little or no loss of engine efficiency. Vehicles that use the gas are entitled to an exemption from London’s Congestion Charge (http://www.cclondon.com).

But there are disadvantages, too. A conversion will mean that some space in your car’s boot will be taken up by an LPG tank. Vehicles that run on the gas are currently not allowed through the Channel Tunnel, and only about 10% of British service stations presently offer the green fuel.