If you drive a diesel car, you might wonder:
"Are fuel additives necessary for diesel?"
"What types of diesel additives are there?"
"What are cetane booster additives?"
"What's different about diesel additives for winter use?"
Diesel fuel additives are products added to diesel fuel to enhance specific performance aspects.
However, not all diesel fuel additives are designed for the same purpose.
Some focus on injector cleanliness.
Others target ignition performance.
Some assist with fuel system lubrication.
Some address low-temperature fluidity.
And some aim for fuel stability and corrosion protection.
The role of additives varies by type.
This article will clearly explain what diesel fuel additives are, their main types and purposes, and considerations when choosing them.
How Do Diesel Engines Ignite, Anyway?
Gasoline and diesel engines differ in how their fuel is ignited.
Gasoline engines typically use a spark plug to ignite the air-fuel mixture.
In contrast, diesel engines self-ignite by injecting diesel fuel into a combustion chamber where air has been highly compressed and heated.
Therefore, for diesel fuel, several performance aspects are crucial:
How appropriately it can self-ignite.
How finely the fuel can be atomized.
Whether it flows properly even at low temperatures.
Whether it provides sufficient lubrication for the fuel pump and injectors.
The Petroleum Association of Japan also explains that diesel fuel requires appropriate ignitability, low-temperature fluidity, and adequate viscosity/lubricity to prevent wear in the fuel injection pump.
What Are Diesel Fuel Additives?
Diesel fuel additives are products added in small amounts to diesel fuel to enhance or adjust specific performance characteristics.
It's important to note here that:
It's not that "diesel fuel originally contains no additives."
Commercially available diesel fuel is manufactured and adjusted to meet standards, and various additives are used during manufacturing and distribution as needed.
ExxonMobil also explains that cetane improvers, lubricity improvers, 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 normal fuel."
Instead, they should generally be considered as something to add based on your purpose and usage environment.
Type 1: Detergent Additives
In diesel engines, fuel is injected very finely from the injectors.
Especially in modern common rail diesels, fuel is injected at high pressure, and the combustion state is precisely controlled.
Therefore, the injection state of the injectors is critical.
Detergent additives target deposits accumulating in injectors and other components, aiming to maintain the cleanliness of the fuel injection system.
Chevron and ExxonMobil also describe detergent additives for diesel fuel as products intended to remove or prevent injector deposits.
While many tend to think of fuel additives as something that "increases horsepower," in reality, many products are designed for condition maintenance like this.
Type 2: Cetane Improvers
When researching diesel fuel, you'll encounter the term "cetane number."
The cetane number is an indicator of a diesel fuel's self-ignition quality.
Generally, a higher number indicates easier ignition.
It's easy to confuse with the "octane number" used for gasoline, but their meanings differ.
Gasoline's octane number indicates resistance to knocking, an abnormal combustion.
Conversely, for diesel fuel, the key is "whether it can self-ignite properly in compressed air."
ENEOS also explains cetane number as an indicator of diesel fuel's self-ignition quality, stating that a higher number means the fuel 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 startup. However, the magnitude of the effect varies depending on the engine and fuel.
Is a Higher Cetane Number Always Better?
It's not appropriate to simply assume that:
"The higher the cetane number, the better the performance."
Vehicles are designed assuming a certain fuel quality.
Furthermore, the effect of cetane improvers doesn't increase proportionally as the additive amount increases.
Chevron's technical documents also explain that for typical cetane improvers, the effect gradually diminishes as the additive amount increases.
What's important is:
Meeting the required fuel quality.
And burning in a state suitable for the vehicle.
Type 3: Lubricity Improvers
Diesel fuel doesn't just burn.
In fuel systems like fuel pumps and injectors, the lubricity of the diesel fuel itself is also crucial.
Especially in high-pressure fuel pumps, highly precise parts operate under high pressure.
Therefore, diesel fuel requires lubricity to protect the fuel system.
The Petroleum Association of Japan also lists adequate viscosity and lubricity, necessary for preventing wear in the fuel injection pump, as one of the quality requirements for diesel fuel.
Lubricity improvers are designed to supplement the lubricating performance of such fuel systems.
However, commercially available diesel fuel is supplied meeting the necessary standards.
Therefore, it doesn't mean that all cars need additional lubricity improvers 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 within it can precipitate.
If this progresses, it can lead to problems such as:
Clogged fuel filters.
Reduced fuel flow.
Inability to supply enough fuel to the engine.
In the worst case, engine stoppage.
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 available diesel, it could lead to problems such as engine stoppage.
Cold flow improvers are additives designed to improve fluidity when wax precipitates at low temperatures.
Is it safe to just add a diesel additive in winter?
Care is needed here.
If you're going to a cold region, instead of thinking:
"Adding an additive to summer diesel will solve everything."
The basic approach is to first refuel with diesel suitable for the season and region at your destination.
Furthermore, the performance of cold flow improvers varies depending on the temperature, concentration, and compatibility with the fuel.
ExxonMobil also mentions that aftermarket cold flow improvers may not interact well with additives already blended into the fuel, and under certain conditions, they could even worsen filter clogging.
In other words, rather than:
"Just put something in because it's winter."
The correct order is to:
Use diesel fuel appropriate for the region.
Only use compatible products when necessary.
Follow the usage instructions.
Type 5: Additives for Fuel Stability and Corrosion Protection
Diesel fuel is also affected by air, temperature, moisture, and other factors during storage.
Therefore, the long-term condition of fuel can become an issue in facilities that store fuel for extended periods, or in:
Agricultural machinery.
Construction machinery.
Emergency generators.
Ships.
In such applications, additives targeting:
Oxidation stability.
Corrosion.
Moisture.
Fuel system contamination.
may be used.
Chevron categorizes the uses of diesel fuel additives into engine/fuel system performance, fuel handling, fuel stability, and contaminant control, among others.
This approach is particularly important not only for cars but also for machinery that stores fuel for extended periods.
Can Diesel Additives be Used in DPF-Equipped Vehicles?
Modern diesel vehicles are equipped with advanced exhaust gas purification devices such as DPFs.
Furthermore, they incorporate:
High-pressure common rail systems.
Precision injectors.
Various exhaust after-treatment devices.
Therefore, when choosing an additive, it's crucial not to simply judge by the label "for diesel" but to confirm if it's suitable for your vehicle.
Especially for DPF-equipped vehicles and the latest diesel cars, it's safer to use an additive only after checking:
The vehicle manufacturer's precautions.
The additive manufacturer's compatibility information.
The correct usage concentration.
If compatibility cannot be clearly confirmed, please consult with the dealership or product manufacturer.
Do Diesel Additives Need to Be Added Every Time?
This varies depending on the product.
For example, there are:
Detergent additives to be used at regular mileage intervals.
Cold weather products for use under specific conditions, such as in winter.
Types for continuous use at a certain concentration with each refueling.
Therefore, it cannot be uniformly determined that:
"Diesel additives should be used every 5,000 km."
Or,
"They must always be added every time."
As explained in the previous article "Are Fuel Additives Always Necessary?", it is important to:
Determine the frequency of use based on the product's purpose.
How to Choose Diesel Fuel Additives
When choosing, checking these five points will make it clearer:
-
What is the purpose of use? Clarify the objective, such as cleaning, ignition quality, low-temperature performance, lubrication, or fuel conditioning.
-
Confirm official compatibility with diesel fuel.
-
Confirm compatibility with your vehicle, especially DPF and common rail systems.
-
Check the dosage and frequency of use.
-
Confirm if it can be used in conjunction with other fuel additives.
What you want to avoid most is:
Adding various additives with different purposes one after another just because "it seems good for a diesel car."
Will Adding More Additive Increase the Effect?
Generally, it is not recommended.
Fuel additives have an appropriate concentration for each product.
For example, even with a cetane improver, the effect does not continue to increase proportionally as the amount added increases.
For cold flow improvers, the combination with the fuel and the usage conditions are also important.
Care must also be taken when combining multiple additives without a plan.
Chevron also emphasizes that for diesel fuel additives, it is important to understand the problem or purpose and use them according to the recommendations of the engine manufacturer and additive manufacturer.
Diesel Additives Cannot Fix Mechanical Failures Alone
For example, if you experience symptoms like:
Engine warning light illuminated.
Sudden increase in black or white smoke.
Significant power loss.
Unstable idling.
DPF warning light won't turn off.
Fuel leak.
Inability to start.
In such cases, inspection is necessary before trying an additive.
Mechanical or electronic causes, such as:
Injector or fuel pump failure.
Sensor malfunction.
EGR or DPF issues.
Poor compression.
cannot be repaired with additives.
Fuel additives are not a substitute for maintenance but one means of conditioning to be used according to their purpose.
Can Gelhorn Be Used with Diesel Fuel?
Next Science's Gelhorn is also compatible with diesel fuel.
Current product information states compatibility with three types of fuel:
Gasoline.
Diesel.
Kerosene.
Gelhorn is not a product designed to adjust only one specific parameter of diesel fuel, like typical cetane improvers or cold flow improvers.
Next Science positions it based on the concept of fuel conditioning, which means:
"Conditioning the fuel and stabilizing combustion."
The guideline for usage amount is:
0.5 ml per 1 liter of fuel.
For example:
10 ml for 20 L.
20 ml for 40 L.
30 ml for 60 L.
PEA-based Cleaners and Gelhorn Have Different Purposes
As explained in the existing article "What are Fuel Additives?", not all fuel additives take the same approach.
Typical PEA-based detergent additives primarily aim to tackle deposits on:
Injectors.
Combustion chambers.
Intake valves, etc.
On the other hand, Gelhorn focuses on the fuel itself and the combustion state.
Therefore, instead of comparing "which is superior," it's crucial to choose based on:
What your intended purpose is.
The same applies to diesel vehicles.
Understanding the Quality of Diesel Fuel Itself is Also Important
When thinking about diesel fuel additives,
It's easy to focus solely on the additives.
However, what's important first and foremost is the diesel fuel itself.
Diesel fuel sold in Japan has standards for ignitability, fluidity, viscosity, sulfur content, and more.
Furthermore, diesel fuel with low-temperature performance suitable for the region and season is supplied.
In other words:
First, use appropriate diesel fuel.
Maintain your vehicle correctly.
Then, consider additives for necessary purposes.
This order is fundamental.
Summary: Choose Diesel Fuel Additives by "Purpose"
There are various types of diesel fuel additives.
Detergent.
Cetane improver.
Lubricity improver.
Cold flow improver.
Fuel stability and corrosion protection.
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 do you want to improve or maintain?
Can it be used in your vehicle?
How much should you add?
How often should you use it?
And, current diesel fuel itself is supplied meeting certain quality standards.
Fuel additives are not a substitute for proper diesel fuel or basic maintenance.
Using appropriate fuel and maintaining your vehicle correctly.
Then, choosing additives based on your necessary purpose.
This is the fundamental approach to correctly utilizing diesel fuel additives.