According to Murray Walker

A season of F1 and testing consumes less fuel than one 747 flying across the Atlantic. I can't verify that but a search online suggests he's been making this comparison for at least two years. But I have found a comment to an article describing the F1 as the world's dirtiest sport that sorta agrees:

50 tons of carbon emissions works out to burning the equivalent of about 20,000 litres of gasoline. That is a lot for 1 car, but probably about the same as any 10 single-passenger vehicle commuters (even in reasonably efficient cars) might burn in a year. And keep in mind that a 747-400ER has a fuel capacity of over 200,000 litres. One 747 flight from Vancouver to Australia will burn about as much fuel as TEN F1 cars running all season!

Whether it's all true or not, just finished listening to an awesome interview with the legendary commentator. It'll be available as a podcast later today.