I have recently bought a petrol lawnmower. I am a bit concerned where my fuel disappears to? I have filled it to max and cut my front and back grass. When I store it in the garage there is a string smell of fuel. There is no leak on the floor. After about 3 or 5 days the tank is completely dry. It's like I've never put fuel in. I've had to fill it 3 times so far. Please help.