The other day I filled the tanks up full before going to mow. I was on a job, on a hill, with no trees, it was 92 degrees. I filled them up to about an inch below the neck. About 1 o'clock, I started to smell gas, I turned around and the tank I wasn't using was spewing gas out. You could see the tanks literally "breathing". Those black tanks get really hot. Just going to let everyone know as summer gets here you can't fill them all the way up if there is no shade where you are going to be mowing.