This week on The Best of Car Talk, Ivan went for an oil change, and was told he needed a special detergent beause his oil was clumpy. Did his oil change guy base this on a close examination of Ivan's engine, or a quick guess on Ivan's gullibility? Also, can $170 be too much to spend on a dream car? In the case of the truck Michelle's husband just bought her, it might be. Can Tom, Ray, and a few thousand rolls of duct tape re-kindle Michelle's passion? Find out, this week on The Best of Car Talk.