Liquefied petroleum gas may sound cranky, but it could be the best future for the enthusiastic driver

When Gordon Brown got up in the House of Commons the other day to deliver his Pre-Budget Report he said something that was truly terrifying. No, it wasn't the bit about him borrowing £176,000,000,000 over the next six years. Nor was it when he discussed the Gershon review of public sector efficiency, which sounds deeply ominous. Nor even was it when he started talking about mucking about with the housing market.

No, the really worrying passage in Mr Brown's address for those of us who like our motors and who like our planet and want to do our bit to save it concerned his proposals for "green fuel". And I quote: "I propose also to consult on a new framework for the tax treatment of green fuels: that we make a commitment to prior announcements, three years ahead, of incentives to increase usage and thus promote investment in new fuel- efficient technologies."

In the accompanying press release from HM Treasury I found the following still more chilling words: "In order to develop the Government's environmental strategy the Pre-Budget Report announces the establishment of an alternative fuels framework to guide the duty regime for alternative fuels; a gradual increase in the duty rate of liquefied petroleum gas to a level which better reflects its relative environmental benefits."

Got that? An increase in the price of LPG to "develop the Government's environmental strategy"; a finer piece of political double-speak couldn't be invented. It is a great pity, because the case for drivers turning to LPG is, or was, an extremely powerful one, and still could be if Mr Brown would only resist the temptation to lob another grenade at the long-suffering British motorist. So let try to me explain why, even with Mr Brown's twitching, tax-grabbing fingers, LPG might still be a good idea for you. I speak as a convert.

I had always thought, perhaps like you, that LPG was a rather cranky sort of thing to be "into". With reason. When I was at school we had a chemistry teacher who resembled the "nerdy professor"played by Griff Rhys Jones in those Vauxhall ads. He had one of those beards-without-a-moustache arrangements that, when combined with a bald pate, makes the wearer look as though he's accidentally put his head on upside down that morning. Anyway, back then, after the great oil shock of '73, our chemistry teacher had his blue 1967 Rover 2000 converted to LPG, and we all thought it, well, a bit cranky and the sort of thing that only a chemistry teacher from Leicester would go in for. We were right.

It wasn't long before he was explaining that LPG is the generic name for commercial propane and commercial butane. These are hydrocarbon products produced by the oil and gas industries. Commercial propane predominantly consists of hydrocarbons containing three carbon atoms, mainly propane (C3H8). Commercial Butane predominantly consists of hydrocarbons containing four carbon atoms, mainly n- and iso-butanes (C4H10).

They have the special property of becoming liquid at atmospheric temperature if moderately compressed and reverting to gases when the pressure is sufficiently reduced. Advantage is taken of this property to transport and store these products in the liquid state, in which they are roughly 250 times as dense as they are when gases. I got a B in my O level, you know.

But 30 years on, and - hey presto - last week I found myself driving the spiritual successor to the Rover 2000, a Rover 75 in Tourer form with, yes indeed, LPG power. How spooky is that?

Now, I'm no crank, and I don't have a funny beard, but I do have to declare that LPG is great. The 1.8 litre Rover 75 drove like any other of its ilk, that is to say a little underpowered, but with an excellent chassis and a classy cabin. The (additional) LPG tank occupies the space normally given over to the spare wheel in the boot (a can of expanding rubber polymer is provided to deal with punctures). So there's no sacrifice of versatility or space. As a dual-fuel car it was possible to compare petrol and LPG performance on the move at the press of a button and there was no discernible difference. The car starts on petrol and then, after a few minutes, switches itself over to LPG, unless you determine otherwise.

Filling up an LPG vehicle is a slightly unfamiliar experience, because the nozzle has to be locked into the LPG tank, but you soon get the hang of it. Of course, there are only about 1,000 places to refuel on LPG, but with a little planning most city dwellers ought to be able to organise their way around that. And don't forget that most LPG cars are dual fuel and run perfectly happily on petrol if you run out.

LPG has far lower emissions and, crucially, and unlike some electric cars, the energy involved in making the LPG and transporting it is less than for conventional fuels. In the jargon of the trade, the "well to wheel" energy costs of LPG are low, not least because it is mostly a by-product of natural gas and does not incur the energy-intensive costs of refining.

The immediate benefit to the driver is financial. At 38p or so per litre, LPG is about half the cost of petrol or diesel. The cost of converting an existing car or the extra cost of buying new has to be weighed against that impressive saving. In the case of the Rover 75 1.8 Tourer, for example, the gross cost is £2,195, minus a grant from the government of about 60 per cent of that cost.

Recognised conversions of cars less than five years old also qualify for a grant, but more typically of, say, 40 per cent, the grant varying according to the age and type of vehicle. As you can probably guess, the bigger the engine and the more miles you do the more economic sense it is going to make to convert to LPG. Not for nothing did John Prescott run one of his Jaguars on LPG, or HM the Queen have her Rolls and Bentleys made LPG-compatible.

Insurance premiums are the same for LPG. They are also exempt from the congestion charge. Volvo, in particular, Vauxhall, Ford, MG Rover, and Peugeot all offer a range of dual-power vehicles, and most makers will have something available. The "advanced calculator" on the Powershift site will help you work out the savings you could achieve, new or used (

It is still a minority sport; there are just 100,000 LPG vehicles on the road, mainly run by local authorities and other fleets, but that is quite a change from four years ago, when a mere 4,000 were registered. Remember when diesel power was confined to lorries and a few taxis?

There are snags. Some underground car parks in France and Italy don't like LPG cars and won't let them in. You can't take an LPG car on Eurotunnel. If you do get to Europe you may find the nozzle at the petrol station is not compatible with your vehicle filling-point, and you may or may not be able to obtain an adapter at the petrol station.

As the LPG fuel tank runs down you may find your car a little more prone to stalling. Safety in an accident is sometimes cited as a problem, although all those involved in the LPG industry are adamant that the extra-tough pressurised LPG tank is safer than a petrol tank.

But the real problem is the Government and its agencies. Not only do we have Mr Brown's unknown intentions to contend with, but Powershift seems to have run out of money for conversion grants, in England and Wales at any rate. No more grants will be dished out until next spring. By which point Mr Brown may have relented. Then there might, just might, be a bit of a scramble. Place your order now, and save the planet. It's not cranky. Honest.

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