Fuel Additives Part 1 - What is Octane Number? How to Increase the Octane Number of Gasoline

Before explaining how to increase octane
What is octane number? Please skip this section if you do not need it.
What is the octane number of gasoline?
Characteristics of gasoline

Gasoline is such a useful physical property that it seems like God created it for engines.
Despite its high energy density and taxation, it is cheap as a retail liquid, thanks in part to its consumption and supply chain, but also to the fact that it can be extracted so abundantly.
(Although the price has risen considerably in recent years, it is cheaper than bottled tea, soft drinks, liquid detergents, etc., and about the same as a carton of milk.)

The most important characteristic of the product is its ignition point, which is high temperature.

The flash point is the temperature at which gasoline will start to burn if a fire is brought close to it or if it is discharged or sparked.
Gasoline ignites at minus 40°C or so.

However, the flash point of gasoline itself is the temperature at which it spontaneously combusts.
420~520℃!

There is a difference of about 500 degrees Celsius!
Of course, there are many substances with a greater difference.
But there is no other substance that can be extracted in such abundance that can be used by people all over the world except for gasoline.

This property allows gasoline engines to start even in the middle of winter, except in some extremely cold regions.
Gasoline injected into a hot engine does not start burning on its own, and the energy can be used efficiently.
If the ignition point, the temperature at which gasoline starts to burn on its own, is too low, the engine will not run properly, or in the worst case, will break down.
This is why a specified octane rating is necessary.

What does octane mean? What does "octane" mean?

The range of 420-520℃ is due to the method of measurement and the quality of the gasoline.
Gasoline is made by heating and distilling petroleum and separating the product near the temperature at which gasoline liquefies, so it contains a mixture of various components.

Among them, isooctane is a simple substance with a high auto-ignition point. The auto-ignition point of gasoline with 100% octane, or technically speaking, the degree of abnormal combustion (knocking) in the engine is called the octane number, which is based on the octane number 100.
(The details are more complex and this is a simplified explanation.)

How to increase octane?
 How can we do this?

The quickest and most obvious way is to mix in something with a high octane value.
Benzenes such as benzene, toluene, and xylene
Alcohols such as methanol, ethanol, and isopropanol are well known for their octane numbers, which range from 110 to 120.

In order to increase the amount of benzene in the gasoline, a process called reforming is used to reform gasoline under high temperature and pressure under a catalyst.

Some countries sell gasoline with methanol or ethanol added, not only to increase octane, and in Japan, ethers are also mixed in.

However, these methods may be difficult to perform by individuals.
Toluene and xylene are relatively easy to obtain, but they must be mixed in large quantities to raise the octane number practically, which is not economical and is not recommended for safety and labor.

The same is true for alcohols, but alcohols also generate less heat and are less expensive.
Methanol and ethanol produce only about two-thirds the heat of gasoline and can cause a loss of power and fuel efficiency.

In Japan, octane rating is mainly obtained with MTBE (methyl tertiary butyl ether).
MTBE has a high heat of combustion and a high octane number, but because it mixes easily with water, its addition is banned in the United States due to concerns about its safety for the human body and its impact on the environment.
ETBE (ethyl tertiary butyl ether), which is non-water soluble and therefore less likely to be released into the environment, is beginning to be used. (However, the toxicity and environmental effects of long-term exposure are unknown.)

Organometallic Anti-Knocking Agents

In the past, tetraethyl lead was added to gasoline as an anti-knocking agent, and even today it is used in aviation fuel, but organic lead is very toxic, and aviation fuel is very expensive and impractical.

But similar organometallic antiknock agents do exist!
Ferrocene, an organic iron compound that we sell, and MMT (methylcyclopentadienyl manganese tricarbonyl), an organomanganese compound that is also sold as a fuel additive product by other manufacturers.

I can't be sure, but in Japan, these compounds are not added to gasoline, or if they are, they are probably used in very small quantities.
If they are, they are probably in very small quantities.
In other countries, depending on the region and the oil manufacturer, gasoline containing them may be available.

Ferrocene is also blended in Asian countries, some parts of Europe, and most notably in Germany, where there are a large number of car manufacturers.
It also appears to be sold in the UK as an alternative to tetramethyl lead (anti-knock and valve seat protection) for classic cars.