In 1971 I was working as a car salesman. It was a Saturday and I had just filled the tank of my demonstration car. I was in the countryside and I had to stop for a cow on the road. However I was on the blind side of a humpback in the road and a Jaguar XJ6 ran into my rear end at high speed. The tank burst. I believe that because my petrol tank was full, the fumes could not be compressed and explode on impact. Perhaps I am wrong but I keep my tank full when out of town. I think I saved my life and I would rather save it than a few quid over a year.