EnviroTerrorists.
They burn down new home developments.
They burn SUV's on dealer lots.
This is a logical step.
Enviro Terrorists is right, says my gut.
I used to work at a gas station. The filler covers can be lifted by hand, and the fuller caps below them never have locks.
It would be incredibly easy for ELF terorists to go there late at night (all lights off), and pour either bags of sugar or gallons of lindseed oil into the tanks. Either one would cause the problem, and kill a car in 3 hours.
Polystyrene is too bulky to use. Think of 10,000 foam cups.
Lindseed oil is chap and effective. A half a cup in a tank will kill your engine permanently. A couple ounces will kill it slowly.