Manufacturers of steel fuel tanks are quick to, point out the two main deficiencies of plastic fuel tanks: higher hydrocarbon emissions and nonrecyclability. Steel has inherent advantages in these areas; nonetheless, durable, lightweight plastic tanks are the design choice in over 70% of North American vehicles. And this market share may continue to rise. While little progress is-being made on the recycling issue, blow-molders and thermoformers are finding ways to reduce evaporative tank emissions just in time to meet more stringent air-quality regulations. "Although plastic seems to have become the material of choice, steel makers raise concerns that [plastic tanks] cannot meet the California Partial Zero Emission Vehicle (PZEV) legislation emissions regulations," note the authors of a recent market study from automotive trade publisher Just-Auto.com. It's true that plastic tanks made with traditional methods cannot meet the PZEV standard, which 6% of all vehicles sold in the state must meet, starting this year. Steel tanks have had little trouble meeting the PZEV limit, which is less than one tenth the level of the previous standard. "In the U.S., the California Air Resources Board certified 23 car models in 2004 as PZEV vehicles: all of these used steel fuel tanks." But, the authors add, this situation may be changing.