Here's a spiffy product for you: A funnel that lets gasoline (or diesel) through but hangs onto any water. It works! I salvaged about 30 gallons of water- and rust-contaminated gasoline from two different vehicles by running it through "Mr. Funnel." All the crud and water stayed in the funnel. This single use more than paid for the funnel.

The instructions tell you to test the funnel before each use by filling it most of the way with water and verifying that it doesn't pass through the filter. It's sort of freaky to see how fast gasoline passes through a filter that's watertight!

I don't understand the physics of this, but assume it has something to do with water having a high surface tension compared to gasoline.