a locking fuel cap will scupper you , unless you do damage to get in, just put liquidized rotten fish into the inlets of the ventilation systems,
herring works well, takes years to go away if not at all, unable to sell the car is just a bonus!!!!
its never been too good as ive been in retail for 30 plus years so they've (the punters) drained all the lifeforce out of me, a bit worse lately though.!