[gsharapa]

It's your gas expanding in the tank as it heats up in your garage in all this hot weather especially if it's close to full. Just like air in your tires expand when they get hot the pressure goes up your fuel expands and the fumes come out the vent tube. Here in Dallas it's been over 100 for 24 days and 105 today. I have two 5 gallon jugs for some 107 fuel sitting in the garage and 1 is half full and every couple of days I open the vent cap and "push" the air pressure is released. If yours is extremely bad you might want to raise your garage door a couple inches during the day...