Fuel for both vehicles and domestic use has been a valuable commodity and now more so with the extremely high oil price on international markets. A typical tank of petrol or diesel is worth £100 or more and a 500 litre tank of domestic central heating oil worth about £500. As a result of the high prices thefts are on the increase.
Ideally cars should be parked in a garage or secure car park. If this is not possible use CCTV or busy areas where theft is less easily committed. Domestic fuel tanks are usually outside these days and so are hard to protect. Use locks on tanks where possible and think about installing CCTV and lighting.
Thieves will go for easier targets. Make it as hard as possible.