You might save a few pounds compared to forecourt prices - but getting caught could cost you your car.
Officers from Downham Market have seized eight vehicles in their last five shifts after they were found running on red diesel.
The fuel, on which a lower rate of duty has been paid, can only legally be used in some farm vehicles.
Police have been pulling over vehicles in the King’s Lynn and Wisbech areas and dipping their tanks to check that they are not running on illegal fuel.
Officers also seized a blue hatchback whose driver was having a nap in a layby with the engine running.
“It’s probably not the best idea to fall asleep in your vehicle on a road in Tilney All Saints with your engine running if you don’t have insurance or a driving license,” one of them tweeted.
“Vehicle seized and driver reported for offences.”
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