Around 800 litres of red disel have been stolen from a locked, towable bowser at a garage in Bognor Regis.
The theft occurred overnight between October 2 and 3 at Chichester Road. It is believed a fairly large vehicle would have been needed to remove the amount of fuel stolen.
A number of diesel fuel thefts have been reported in the west of Sussex recently.
If you witnessed any suspicious activity in the area at that time or have any information about the theft, please call 0845 60 70 999 quoting serial 0231 of 03/10.
Police are advising drivers of lorries to be vigilant when parked up in laybys and to immediately report any suspicious behaviour.
In recent weeks there has been an attempted theft of diesel from a site at Ford and the reported theft of fuel from vehicles in a layby at Westergate, near Chichester.