Very smart of him to put the tracker on the gas tank cap that was being replaced. Although the entire plan was premised on something that any dime store criminal would likely not do. If the thief threw the tracker out the window a block from Mike's house, then it would've been a complete waste of time and money. I don't think most people would've been dumb enough to drive around with the cap after stealing it.
shareI don't think they will realize it is not the correct tracker until they swap the battery, back at their base. then they will see it does not show up on their receiver, but by then it will be too late because Mike will know where they are.
At first I was confused why he was getting the exact same model of tracker instead of just putting their tracker on some random car or something. But he needed them to look identical so eh could track the trackers. Super clever.
I also love that the show cut between Chuck's cunning plot with the tape recorder batteries and Mike's cunning plan with the tracker batteries. Both men are very calculating and intelligent and both can see several chess moves ahead.