I bought a 23 gal. tank from overstock.com for $140. It was made by Moeller and used on Lund boats. In 2011, boat manufacturers were required to install low permeable tanks when they ran out of their older stock. Low permeable tanks have a black nylon lining (as can be seen here). There are still a lot of older style permiable tanks being sold even though they are new old stock and unused. BoatUS did an experiment where they found that an old style 6 gallon plastic outboard tank lost almost a pint in 6 months. That's why gas goes bad.