What are Diesel Fuel Additives? Types, Purposes, and How to Choose Diesel Fuel Additives

When driving a diesel car, you might wonder:

"Do diesel cars need fuel additives too?"

"What types of diesel additives are there?"

"What is an additive that raises the cetane number?"

"What's different about diesel additives used in winter?"

Diesel fuel additives are products added to diesel fuel to support specific performance aspects.

However, not all diesel fuel additives are made for the same purpose.

Some focus on injector cleaning.

Some focus on ignition performance.

Some support the lubricity of the fuel system.

Some address fluidity at low temperatures.

Others aim for fuel stability or corrosion prevention.

Their roles vary depending on the type.

This article will clearly explain what diesel fuel additives are, the main types and purposes of diesel additives, and important points to consider when choosing them.

How does a diesel engine burn fuel in the first place?

Gasoline and diesel engines differ in how they ignite fuel.

Gasoline engines typically use a spark plug to ignite the air-fuel mixture.

On the other hand, diesel engines strongly compress air and then inject diesel fuel into the high-temperature combustion chamber to achieve self-ignition.

Therefore, for diesel fuel, performance aspects such as:

How well it can self-ignite.

How finely the fuel can be atomized.

Whether it flows properly even at low temperatures.

Whether it provides the necessary lubrication for the fuel pump and injectors.

are crucial.

The Petroleum Association of Japan also explains that diesel fuel requires appropriate ignition quality, low-temperature fluidity, and the viscosity/lubricity necessary to prevent wear of the fuel injection pump.

What are Diesel Fuel Additives?

Diesel fuel additives are products added in small amounts to diesel fuel to support or adjust specific performance characteristics.

It's important to note here that:

"Commercial diesel fuel is not originally free of additives."

Commercial diesel fuel is manufactured and adjusted to meet specifications, and various additives are used as needed during manufacturing and distribution.

ExxonMobil also explains that cetane improvers, lubricity enhancers, cold flow improvers, and corrosion inhibitors are used in diesel fuel depending on its application.

This means that additives added to commercial diesel fuel later:

"Are not absolutely necessary to make diesel fuel a normal fuel."

It's generally best to consider them as something to add additionally, depending on your purpose and usage environment.

Type 1: Cleaning Additives

In diesel engines, fuel is injected very finely from the injectors.

Especially in current common rail diesels, fuel is injected at high pressure, and the combustion state is precisely controlled.

Therefore, the injection condition of the injectors is important.

Cleaning additives target deposits accumulated in injectors and other parts to maintain the cleanliness of the fuel injection system.

Chevron and ExxonMobil also describe cleaning/detergent additives for diesel fuel as those intended to remove or prevent injector deposits.

When thinking of fuel additives, many might think:

"They increase horsepower."

But in reality, many products are aimed at maintaining engine condition like this.

Type 2: Cetane Improvers

When researching diesel fuel, you'll encounter the term "cetane number."

The cetane number is an index that indicates the self-ignition quality of diesel fuel.

Basically, a higher number indicates easier ignition.

It's easily confused with the "octane number" used for gasoline, but their meanings are different.

The octane number for gasoline is an index that indicates the resistance to knocking, which is abnormal combustion.

On the other hand, for diesel fuel, it's crucial "whether it can self-ignite properly in compressed air."

ENEOS also explains the cetane number as an index representing the self-ignition quality of diesel fuel, stating that a higher number indicates a fuel that ignites more easily.

Cetane improvers are additives designed to adjust this ignition characteristic.

According to Chevron, within a certain range, a higher cetane number can affect cold startability, combustion noise, and white smoke during start-up. However, the magnitude of the effect varies depending on the engine and fuel.

Is a higher cetane number always better?

It's not always appropriate to simply assume:

"The higher the cetane number, the better the performance."

Vehicles are designed based on certain fuel quality assumptions.

Also, the effect of cetane improvers does not continue to increase proportionally as the amount added increases.

Chevron's technical documents explain that for typical cetane improvers, the effect gradually diminishes when the additive amount is increased.

The important things are:

Meeting the required fuel quality.

And burning in a state suitable for the vehicle.

Type 3: Lubricity Enhancers

Diesel fuel doesn't just burn.

In fuel systems like fuel pumps and injectors, the lubricity of the diesel fuel itself is also important.

Especially in high-pressure fuel pumps, very precise parts operate under high pressure.

Therefore, diesel fuel requires lubrication performance necessary to protect the fuel system.

The Petroleum Association of Japan also lists appropriate viscosity and lubricity necessary to prevent wear of the fuel injection pump as one of the quality requirements for diesel fuel.

Lubricity enhancers are intended to supplement the lubrication performance of such fuel systems.

However, commercially available diesel fuel is supplied to meet necessary specifications.

Therefore, this doesn't mean that all cars need to add lubricity enhancers later.

Type 4: Cold Flow Improvers

For diesel vehicles in winter, the low-temperature properties of diesel fuel are particularly important.

When diesel fuel is exposed to low temperatures, wax components in the fuel can precipitate.

If this progresses, it can lead to problems such as:

Fuel filter clogging.

Fuel becoming difficult to flow.

Insufficient fuel supply to the engine.

In the worst case, engine shutdown.

In Japan, to address this issue, diesel fuel with different low-temperature performance is sold depending on the season and region.

The Petroleum Association of Japan also advises that if you travel from a warm region to a cold region in winter without refueling with locally sold diesel, it could lead to problems like engine shutdown.

Cold flow improvers are additives intended to improve the fluidity when wax precipitates at low temperatures.

Is it safe to just add diesel additives in winter?

Caution is needed here.

When traveling to a cold region,

It's fundamentally more important to refuel with diesel fuel suitable for the local season and region, rather than thinking "adding additives to summer diesel will solve everything."

Furthermore, the performance of cold flow improvers varies depending on the usage temperature, concentration, and compatibility with the fuel.

ExxonMobil also mentions that aftermarket cold flow improvers may not work effectively with additives already blended into the fuel, and under certain conditions, they could even worsen filter clogging.

In other words,

Instead of "just adding something because it's winter,"

Using diesel fuel appropriate for the region.

Using compatible products only when necessary.

Following usage instructions.

This sequence is important.

Type 5: Additives for Fuel Stability and Corrosion Protection

Diesel fuel is also affected by air, temperature, and moisture during storage.

Therefore, for facilities that store fuel for long periods, or for:

Agricultural machinery.

Construction machinery.

Emergency generators.

Ships.

the long-term condition of the fuel can become an issue.

For such applications, additives aimed at addressing:

Oxidation stability.

Corrosion.

Moisture.

Fuel system deposits.

may be used.

Chevron categorizes the uses of diesel fuel additives into engine/fuel system performance, fuel handling, fuel stability, and contaminant control.

This is a particularly important consideration not only for automobiles but also for machinery that stores fuel for long periods.

Can diesel additives be used in DPF-equipped vehicles?

Modern diesel vehicles are equipped with advanced exhaust gas purification systems such as DPFs.

Furthermore,

High-pressure common rail.

Precision injectors.

Various exhaust aftertreatment devices.

are also combined.

Therefore, when choosing an additive,

It's important not to judge solely by "for diesel" and to confirm if it can be used in your vehicle.

Especially for DPF-equipped vehicles and the latest diesel cars,

It's safer to confirm:

Vehicle manufacturer's precautions.

Additive manufacturer's compatibility information.

Concentration of use.

before using.

If compatibility cannot be clearly confirmed, please check with the retailer or product manufacturer.

Do diesel additives need to be added every time?

This varies by product.

For example, there are:

Cleaning additives used at regular mileage intervals.

Low-temperature treatment products used under specific conditions, such as in winter.

Types that are continuously used at a certain concentration with each refueling.

Therefore,

"Diesel additives every 5,000 km"

or

"Always add every time"

cannot be uniformly decided.

As explained in the previous article "What are Fuel Additives?",

It is important to determine the frequency of use based on the product's purpose.

How to Choose a Diesel Fuel Additive

When choosing, checking these 5 points will help clarify:

• What is the purpose of use? Clarify the purpose, such as cleaning, ignition quality, low-temperature performance, lubrication, or fuel conditioning.

• Confirm if it is officially compatible with diesel fuel.

• Check compatibility with your vehicle's DPF, common rail, etc.

• Confirm the usage amount and frequency.

• Confirm if it can be used in conjunction with other fuel additives.

The biggest thing to avoid is:

Adding different additives one after another for different purposes, just because "it seems good for diesel cars."

Does adding more additive increase the effect?

Generally, this is not recommended.

Each fuel additive has an appropriate concentration.

For example, even with a cetane improver, the effect does not increase proportionally as the amount added increases.

For cold flow improvers, the combination with the fuel and usage conditions are important.

Care must also be taken when combining multiple additives indiscriminately.

Chevron also states that for diesel fuel additives, it's important to understand the problem or purpose and to use them according to the recommendations of the engine manufacturer and additive manufacturer.

Diesel additives alone cannot fix malfunctions.

For example, if you experience symptoms such as:

Engine warning light illuminates.

Sudden increase in black or white smoke.

Significant loss of power.

Unstable idling.

DPF warning does not clear.

Fuel leak.

Unable to start.

In such cases, an inspection is necessary before trying additives.

Mechanical and electronic causes such as:

Injector or fuel pump failure.

Sensor malfunction.

EGR or DPF issues.

Compression failure.

cannot be repaired with additives.

Fuel additives are not a substitute for maintenance but one of the conditioning methods used according to purpose.

Can GERHON be used with diesel fuel?

This section describes the earlier GERHON 3+ product, which was compatible with three types of fuel. The new GERHON Fuel Conditioning range has separate products for gasoline, diesel and kerosene. Choose a product by fuel type.

NEXT SCIENCE's GERHON is also compatible with diesel fuel.

The earlier GERHON 3+ product is compatible with:

Gasoline.

Diesel.

Kerosene.

GERHON is not a product intended to adjust just one numerical value of diesel fuel, like typical cetane improvers or cold flow improvers.

NEXT SCIENCE positions it based on the concept of fuel conditioning, which aims to:

"Adjust the state of the fuel and stabilize combustion."

The estimated usage amount is:

0.5ml per 1L of fuel.

For example,

10ml for 20L.

20ml for 40L.

30ml for 60L.

and so on.

PEA-based cleaners and GERHON have different purposes.

As explained in the existing article "What are Fuel Additives?", not all fuel additives take the same approach.

Typical PEA-based cleaning additives primarily aim to address deposits on:

Injectors.

Combustion chambers.

Intake valves, etc.

On the other hand, GERHON focuses on the fuel and combustion state.

Therefore,

Instead of comparing "which is better,"

It's important to choose based on "what purpose you want to use it for."

The same applies to diesel vehicles.

It's also important to understand the quality of diesel fuel itself.

When thinking about diesel fuel additives,

It's easy to focus solely on the additives.

However, what's important before that is the diesel fuel itself.

Diesel fuel sold in Japan has specifications regarding ignition quality, fluidity, viscosity, sulfur content, etc.

Furthermore, diesel fuel appropriate for the region and season is supplied for low-temperature performance.

In other words,

First, use appropriate diesel fuel.

Maintain the vehicle correctly.

Then consider additives for necessary purposes.

This sequence is fundamental.

Summary: Choose Diesel Fuel Additives by "Purpose"

There are various types of diesel fuel additives:

Cleaning type.

Cetane improvement.

Lubricity improvement.

Low-temperature fluidity improvement.

Fuel stability and corrosion prevention.

Fuel conditioning.

Each has a different purpose.

That's why,

"All diesel additives are the same"

is not true.

First, it's important to confirm:

What you want to improve or maintain.

If it can be used in your vehicle.

How much to add.

How often to use it.

And the diesel fuel itself is supplied meeting certain quality standards.

Fuel additives are not a substitute for normal diesel fuel or basic maintenance.

Use appropriate fuel and maintain the vehicle correctly.

Then choose additives according to the necessary purpose.

This approach is fundamental to correctly utilizing diesel fuel additives.