"And if Asda's sales figures were anything to go by, unless he was running a fleet of buses across south Wales, the driver who had been pulled over by the emissions inspectors wasn't the only one. Wind your windows down in a Swansea traffic jam last spring, the rumour went, and the chances were you would think someone was having a barbecue. The local joke was that the whiff was particularly prevalent around the DVLC, the government's national car-licensing department, which is headquartered in the city. It was a nice irony, because, as the cooking-oil driver discovered when he was fined £500 and had his car impounded, the government is not amused by cheap alternative fuel. Diesel is relatively pricey because a large chunk of the cost is made up by duty. Cooking oil carries no such tax. But if it is put to use in a petrol tank, duty is due.
When, in September, just up the coast from Swansea, in Burry Port, near Llanelli, six more drivers were discovered apparently running their cars on cooking oil, the news quickly spread. "It was a media feeding frenzy," says Dai Davies of Dyfed and Powys police, whose officers were involved in the spot checks. "Everyone came down here, from the local BBC news to the New York Times." Within a couple of days, the story was in circulation of a crack team of law-enforcement officers swooping on south Wales motorists, of widespread tax fraud, of a hunt for the Mr Big of the cooking-oil scam."
http://www.sovereignty.org.uk/features/foo...th/biofuel.html
seems you just cant win
you find a way to save a few bucks on fuel and the gov. wants to stop you