Fuel additives

Thomas Midgley Jr.Thomas Midgley Jr.

Fuel additives

Early automotive engines ‘knocked' whenever poor quality gasoline was used. In 1921, Thomas Midgley Jr. used tetraethyl lead as antiknock additive in gasoline to make engines run smoother and quieter. By 1926, an octane rating was introduced to measure the quality of gasoline (compression tolerance). The use of lead additives was discontinued in the 1970s because of environmental concerns.

Chromium-plated engine componentsChromium-plated engine components

Today, small amount of chemicals (alcohols, ethers) are added to gasoline to improve octane rating, enhance gasoline performance (metal deactivators), and reduce engine friction and wear to extend engine life (detergents). Seasonal chemical additives are used in some areas for geographical concerns, such as the addition of methanol to prevent freezing of fuel line.

Table of octane ratings


Did you know?

In the 50s, fuel used in Formula 1 race cars consisted of 45% benzine, 25% methanol, 23% (130 octane) jet fuel, 3% acetone, and some lubricating additives. After each race, the mechanics dismantled and carefully washed the engine, otherwise the fuel would have burnt the wires. Due to the strict regulations, the fuel used for F1 races today is hardly different from the regular unleaded 98 octane one.

Lead tetraethyl molecule