A suspect filled up a silver Vauxhall Zafira, bearing stolen index plates, with £65.26 of fuel before driving off without paying in Northampton.
The incident happened BP garage in Harborough Road, Kingsthorpe at about 4.35pm on Monday, April 3, Northamptonshire Police today revealed.
A spokeswoman for Northamptonshire Police said: "He was white, aged in his 20s with a slim/medium build.
"He had dark facial hair and was wearing a grey baseball cap, a black t-shirt with a printed image, black joggers and white adidas trainers."
Anyone with information about the theft should call Northamptonshire Police on 101 or Crimestoppers, in confidence, on 0800 555111.