A special police unit nicknamed the “frying squad” has been formed in a market town where hundreds of drivers are believed to be running their diesel cars on cooking oil. Sniffing out unusually fragrant exhaust fumes, highway patrols have already collared several dozen offenders, who save more than 40p a litre by diverting oil from the kitchen cupboard to under the bonnet. The Asda supermarket in Llanelli, south Wales, has slapped a ration on cooking oil sales, after astonished internal auditors found that it was selling far more than any other outlet in the country. Customs investigators are also involved...