Dear Doctor: I fill my vehicle’s gas tank every week during my lunch break. I took my co-worker with me last week and he said not to overfill the gas tank. When the nozzle clicks stop do not put any more gas in. I told him I could usually get another gallon in. He said it’s not good, but could not explain why. Is this true? Ray
Dear Ray: Yes, it’s true. When you overfill the gas tank you take a chance of damaging the EVAP system in the vehicle. All late model vehicles have a charcoal canister that can be damaged when the gas tank is overfilled. Remember the gas will expand with heat. You also never want to buy gas when the tank truck is refilling the underground tanks at the gas station. Always buy gas in the early morning or at dusk. There is less vapor loss during these hours.