I feel your pain. My wife has a talent for coming to ask random questions when I'm up to my elbows in the car; "I just wanted to know what kind of bla bla etc. you wanted for X, Y,Z when we go to bla bla bla next week, and so on..." Usually I insist that its not a good time and she ignores me and launches into a series of questions regarding banal minutiae of our lives and I skip a tooth on a cam gear or fry a battery or spill some fluid or something. The moral of the story though is that its your fault for not putting the towel down yourself, you can't blame them for not doing exactly what you want and its only a car.