Many people don't even think about cleaning their car until the weather gets warm, at which point they suddenly realize it's time to hose off that six-month layer of crust on their car, truck, SUV, minivan or station wagon. Actually, if you live in a warm climate, the opportunity to clean your vehicle may last all year long. However, even in mild climates, there's plenty of filth that can build up on a car's paint in just a few short days. Residents of Los Angeles can testify to the fact that even a freshly cleaned vehicle will look dingy and tarnished after only 72 hours of exposure to the city's air. I affectionately refer to this accumulated, grimy substance as "L.A. Atmosphere" and try not to think about its affect on my lungs.