Recently, I have been spilling gas on my fillups because the gas pump just wouldn't stop when the tank is full. It only happens sometimes, not all the time. I was wondering if there's something wrong with my car's fuel tank/neck or is it just the gas station? The spilled gas has discoloured my tires to a brown colour and I am not sure if it is detrimental to the rubber material. Some people on the internet say it is fine while some say that it will deteriorate the rubber and cause cracks over a period of time. Has anyone experienced the same problem?