Have you ever tried using Amsoil UCL in your mower gas? I've been using it with only E0 gas, and it did make a considerable difference for how long my tank lasted; for my lawn (that's probably a lot smaller,) I could nearly mow the whole place without filling up again. If I didn't use UCL, I'd need to re-fill once.
Then again, I was over-treating it at first, which gave a big puff of smoke when the mower started up. I'd put around a capful in 32 oz of gas. This also made it a bit more difficult to start the mower.
For a while now, though, I've been using 1 ounce in 4 gallons of fuel. The fuel doesn't last as long, so I was thinking of going down to 1 ounce for 3 gallons to see how that goes.
UCL should give a slight bit more power to the mower too, along side the E0 gas doing that too.