Identification

• From the early 1920s until the mid-1970s, leaded gas was the accepted standard for fueling automobiles. Lead was added to gasoline to raise its octane level. The higher the octane, the better, because higher octane gas helps prevent knocking in the engine. The leaded gas helped to protect the parts of older car models from excessive wear as well. New cars are now manufactured to be compatible with unleaded gas only.
  
  

Engines Lose Power

• Leaded gas in a car that takes unleaded could cause an engine to lose power. The lead deposits itself into the engine and the muffler, which causes these parts to rust over time. You would have to get more frequent oil changes and standard maintenance performed on the car, such as spark plug changes and repairs to the exhaust systems to keep the car running.
  
  

Catalytic Converters

• Starting in 1975, all new cars had to be manufactured with catalytic converters by law. Catalytic converters help reduce the emissions from the vehicle. Leaded gas degrades the catalytic converter over time, which is why modern cars cannot take this type of fuel.
  
  

Other Effects

• Leaded gas can also be harmful to humans---both the driver of the car and pedestrians. When the car releases its fumes into the air, it contains lead elements that can enter the lungs and cause damage to the nervous system, especially in children. Kids who have lead in their blood can suffer from behavioral and mental disorders. Adults who inhale too much lead can have problems with high blood pressure.
  
  

Considerations

• Leaded gasoline is not available for sale in the United States. The government started phasing it out in 1973, cars manufactured in 1975 and later had to be more emissions friendly and, in 1996, leaded fuel was banned completely. So you are not likely to make the mistake of putting leaded gas in your car by accident. U.S. gas stations are required to carry unleaded gas and diesel fuel only. Cars that were manufactured before 1975 can be fueled with unleaded gas now as well, but preferably a premium 92 octane gas or higher.