Q: What is Unleaded Gas?

December 17, 2013 12:53 PM

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Whenever you pull up to the pump and see the signs indicating what type of fuel is available, you will likely see mentions of unleaded gasoline. Gasoline is the fuel in your engine that provides the power needed to make your car move. As automobile engine technology develops, so too does the fuel you use to power it. Nowadays, virtually every car on the road is powered by unleaded gasoline. Simply put, unleaded fuel is gasoline that has no lead additives. Lead exposure can cause serious health problems, such as brain damage, especially in children. After the harmful side effects of lead were discovered, it was no longer used in gasoline. In order to understand why it was used, you first need to understand the basic mechanics of an internal combustion engine.

An internal combustion engine works as a system of valves and pistons connected to a crankshaft, which turns the drive shaft and makes the wheels rotate and move the car. First, a cylinder containing a piston and valves. On the "intake" stroke, the space not occupied by the piston draws in a gasoline-air mixture. Next comes the "compression" stroke wherein the piston compresses the air-fuel mixture. The spark plug creates an electrical charge that ignites this mixture, causing it to explode. This explosion pushes the piston and causes the crankshaft to turn. Finally, the piston compresses the burnt air-fuel mixture and pushes it out of the cylinder through the open exhaust valve or valves. Then the cycle starts again.

Because these parts are made of metal, the constant rubbing can produce excessive friction and damage the engine components. Lead acted as a lubricant. In the process, however, it leaves harmful residue in engines that reduce performance and could ultimately destroy the engine. If fuel spontaneously ignites in the cylinder rather than from the spark plug, this is called "knocking" and can damage the engine due to out-of-rhythm firing. Lead increased the anti-knocking properties of a fuel. In the U.S. leaded fuel for on-road vehicles has been banned since 1996.

If you decide to buy an older second-hand car check with the owner to see what type of fuel it uses. Before you can legally drive a vehicle, you may need to have it pass an emissions test. Cars that use unleaded gasoline are more likely to pass an emissions test than ones that do not.

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