Customers have reported engines cutting out and not restarting. Diesel is currently unavailable at the filling station but will return following "thorough testing", Asda said.
Lee Clark, 52, who is a company director of a cleaning and maintenance company and lives in Cardiff, is a regular customer at the Coryton station and is one of the affected customers. He filled up his Range Rover with about £120 worth of diesel on December 27, before driving from Coryton to Cwmbran. But about 15 miles into the journey he said his engine management light came on and faults started coming up.
Fleet Fuel tests provide simple on-the-spot diesel tests for fuel quality assurance, without the need for expensive lab testing.