I had a 5 gallon can of gas stolen out of the bed of my truck several years ago while working in the bad part of town. I waited a couple of weeks and got another 5 gallon gas can full of gas. Only this time, I dumped a half a bag of sugar in it. It only took a couple of days for that can to get stolen but it was a satisfying feeling knowing that I locked up the thieves motor this time.