Pump. And yes. There does seem to be a difference. Even a difference between stations. The problem with all alcohol is that it will absorb water from the air over time. Newer the better. As well as don't leave in tank or carb bowls for extended period of time. A month seems to be ok. It also evaporates faster than even water. Thus even higher H2O percentage over time. This is some what true for gas too. But not as dramatic.
Like everything in performance. Always a cost!
