Well, it has been debated to death. Google id your friend.
You could buy a UV protection filter. It appears to be clear and can protect from fingerprints. Some people say that if you knocked/dropped your lens then the filter would take the damage and tyour precious front lens element will be saved.
IMHO, a lens hood is a must. Good for contrast and offers best protection.
In 10 years of taking pictures, I have always had a UV filter on my lenses but have yet to damage any of them. Go figure!
If you want to go down the UV filter route, and your lens is expensive, you probably wanna pay for a decent filter and not some £10 jobby. Look out for Hoya Multicoated, B+Q etc.
AFAIK, there aren't any filters that will make your motorsport pictures look considerably better. That's up to you.