This week on The Best of Car Talk, Greg was surprised when his truck started running poorly, until he learned that his four-year-old son had washed the inside of the gas tank with soap. Should Greg stick his kid with the repair bill? Elsewhere, Judy can't decide if her son-in-law is brilliant or wacko for raising the hood of his Volvo after every drive; Gil's Camry may be leaving a trail of clutch fluid from Houston to Phoenix; Debra's knocking is nothing compared to the sound of two hosts banging their heads together trying to figure out what's causing it; and, what does Gavin's car have in common with King Tut's tomb? All this and more, this week on The Best of Car Talk.