Stant locking gas caps are OEM quality both in construction and materials as well as deterrent to fuel theft and vandalism. A gas/fuel cap performs three very important functions; safety of the vehicle's occupants, fuel economy and reduce emissions. Safety: Without a fuel cap, gasoline vapors will be present around your car at all times. Those vapors can be ignited by a random spark or flame and are very dangerous if you are involved in an accident or rollover. Fuel Economy: According to Sun Oil Company research, a vehicle with a missing or inoperative fuel cap will allow 176 pounds (22 gallons) of gasoline to evaporate over the period of one year. Emissions: Gasoline vapors emit hydrocarbons which dissolve the earth's ozone layer and cause smog.