This week on The Best of Car Talk, Paul’s Jetta lost some of its Fahrvergnügen, so he tried to pep it up with a new set of spark plugs. Now the car is running worse. Did Paul need more than just plugs or did his mechanic assign the job to the wrong guy? Elsewhere, Joan and her friend are arguing over whether slower highway driving leads to longer engine life; Linda is concerned that Tom and Ray’s “potato in the tailpipe” stalling technique could kill a dog that happened to lock the car doors; and did Helen’s truck really lose 100 miles per tankful of gas, or was she suffering from Move Euphoria? All this and more, this week on The Best of Car Talk.