Small Engines (Lawn Mowers, etc.): gas leaking from vent hole, vent hole, gas leaks

Question
Gravely Promaster 48z.  Gas leaks from vent hole and runs down side of gas tank towards muffler.  Dealer has replaced caps, no help.  Now says Fault is: type of gas, harmonic distortion from engine, wants to detune engine so it runs smoother.  This is a dangerous condition

Answer
Have you tried not filling your fuel tanks, so full?  Gasoline needs  to expand as the ambient temperature increases that's why the fuel cap vents the fuel system.  About the only other way fuel would run out the fuel cap vent is the unit being operated on a steep hill with the fuel tank being on the down hill side.  Depending upon how much fuel is in the tank the Englewood cause the gas rise in the neck of the fuel tank and spill out the vent.  If this is the case you will have to run with less fuel in the tank when you're on a hill or mow only with the tank on the uphill side.  As far as being a dangerous situation any time there is a fuel leak there is the danger of fire.  You should be concerned, but the system has to be vented.  I'm sorry, I do not have better information for you but in my experience this has been the situation.