The bandit pulled his truck to the back of a Burger King in Northern California one afternoon last month armed with a hose and a tank. After rummaging around assorted restaurant rubbish, he dunked a tube into a smelly storage bin and, the police said, vacuumed out about 300 gallons of grease.

The man was caught before he could slip away. In his truck, the police found 2,500 gallons of used fryer grease, indicating that the Burger King had not been his first fast-food craving of the day.

Outside Seattle, cooking oil rustling has become such a problem that the owners of the Olympia Pizza and Pasta Restaurant in Arlington, Wash., are considering using a surveillance camera to keep watch on its 50-gallon grease barrel. Nick Damianidis, an owner, said the barrel had been hit seven or eight times since last summer by siphoners who strike in the night.

“Fryer grease has become gold,” Mr. Damianidis said. “And just over a year ago, I had to pay someone to take it away.”