That shot looks pretty pleasing to me! The car is sharp and the background and foreground are suitably blurred to indicate the car was hurrying! Just chasing up points from earlier, the main thing about f2.8 or f4 lenses is not just that they can take pictures in subdued light, but that they use that faster max aperture for focussing every shot, which really matters in sport. The more light received by the focussing module - the more quickly and accurately it can respond, so a higher percentage of your shots will be in focus. Your 18-200 zoom is a great lens for general out-and-about photography, really the only lens necessary on a long holiday, for example. The Canon one is quite new, and tests by the prestigious French magazine Chasseur d'Images suggest it outperforms the older Nikon equivalent, which we use. But at 200mm they are both f5.6, so an f4 lens is letting twice as much light onto that focussing module - and an f2.8 lens is letting 4 times as much! When a car is approaching you at 150mph, getting the focus right does help a little.....
