Car fuel tanks have traditionally been made of steel but in recent years more gas tanks are being made of plastic, which is lighter and often safer. Placement of the gas tanks is crucial for safety.
Steel gas tanks are generally coated with zinc or with terne, a combination lead and tin. Auto manufacturers mold them into different shapes depending on the vehicle they're designed for. Steel tanks may be safer than plastic tanks in the event of fire because they do not sag or soften in a fire and do not create smoke when burning.
Plastic gas tanks are often the choice of auto manufacturers because they add less weight to the car, helping with gas mileage. They tend to be safer in crashes because they are seamless; they won't burst at the seams under pressure. Plastic high-density polyethylene tanks resist rupture as much as do steel tanks.
Regardless of the material of its manufacture, the most important safety factor for gas tanks is their placement. Fuel tanks placed between the rear tires provide safety in side collisions. A firewall should protect the rear seat from the fuel tank.
