#1939: If That's What It Is This week on The Best of Car Talk, Anne's mechanic can't identify the gunk blowing out of her car's ventilation system, but he does know that whatever it is, fixing it will cost $1000...if that's what it is. Sounds like a new mechanic's mantra to us! Elsewhere, Linda is still trying to figure out how a gas attendant put her radiator cap on backwards; Alan is baffled by the diamond patterns he sees on rear windshields, especially when he's wearing polarized sunglasses; and is Andy safer keeping his doors locked while driving on the highway? And, has our pal Daniel Pinkwater found his true calling, as a scientific measurement? All this and more, this week on The Best of Car Talk.