You pull up to a gas station and, wow, their price is like 30cents less then all the other stations in town so why not fill your tank up, and up, and up? “I’m just trying to squeeze the last bit of that $50 bill into the tank,” you think to yourself. There is a very simple explanation and it is understandable that most people do not know the repercussions of putting in that extra half a gallon or so.
The Fuel at the gas station is stored under ground and it kept quite a bit cooler then the air outside. On a warm or especially hot day this fuel expands once it’s in your tank and needs a place to expand to. In the “Olden Days” the fuel would just go out an over flow tube and leak right onto the ground, you would waist a little gas but not a big deal right? Now most cars especially California Emissions vehicles have products to filter carcinogens, un-burned gasoline fumes and other toxins from leaking into the atmosphere one specific product is an Evaporative Canister. When there is too much fuel, or the fuel needs a place to expand to it will go into this canister and a little down the line this canister will start to malfunction. Your car will be unable to filter these toxins, causing a check engine light to come on, polluting our atmosphere and costing you quite a bit to replace it. On top of that the fuel going into this canister isn’t even being used to you are wasting that fuel and in turn wasting a lot more money.
Once the pump stops, stop fueling your car.