Get a real shammy made of chamois leather not one of the new synthetic imitations. First, a shammy can be used to collect water or dew off plants in a survival situation. But probably the best use of a shammy is to filter gasoline. It is a good expedient fuel/water separator.
It has been used by pilots and boaters for many years to filter water out of gasoline. When a shammy is soaked with clean gasoline, it will not allow water to pass through its surface fibers. Take a large funnel and drape the shammy inside it to form a bowl. Pour the gasoline through the gasoline soaked shammy. Stop if you start to see water accumulating, remove the shammy from the funnel being careful to keep the gasoline and water separate. Dump the water and start over, continue until the gasoline is all filtered.
I would recommend filtering any old gasoline through one is a survival situation. This is something you should consider adding to your vehicle kit.