Diesel Fuel Additives Frequently Asked Questions

Diesel Fuel Treatments Frequently Asked Questions

An informed choice is the best choice. These FAQs will answer the most popular questions about our Diesel Fuel Treatments.

Frequently Asked Questions

Diesel and Diesel Additives 101 FAQ #1

What is Diesel and how is made?  Diesel is one of many products that are produced by a refinery.  A refinery receives a barrel of crude oil and puts it through a series of processes (Distillation, Hydrotreating, and Hydrocracking) to create diesel fuel.  Depending on how the diesel has been refined, there are five key types of diesel fuel in the US:

No. 1 Diesel Fuel: A light distillate fuel oil that It is used in high-speed diesel engines, such as those in city buses and similar vehicles.

No. 1 Fuel Oil: A light distillate fuel oil used as fuel for portable outdoor stoves and portable outdoor heaters.

No. 2 Diesel Fuel: A fuel that is used in high-speed diesel engines, such as those in railroad locomotives, trucks, and automobiles.

No. 2 Fuel oil (Heating oil): A distillate fuel oil that is used in burners for domestic heating or for moderate capacity commercial/industrial burner units.

No. 4 Fuel: A distillate fuel oil is used extensively in industrial plants and in commercial burner installations that are not equipped with preheating facilities.

In the US, the majority of the diesel is No.2 (60 Billion gallons) and used on-road transport fleets (73% of market).  No. 1 Diesel Fuel is also used as a blend component in No. 2 diesel  to help improve the winter performance of the fuel as it contains little to no wax, thus reducing the chance of fuel gelling.

I have seen the term “ULSD”…what does that mean?  ULSD stands for “Ultra-Low Sulfur Diesel” and it is named in this way to indicate that the amount of sulfur in the fuel is very low (15 parts per million).  The US Government has stipulated the use of ULSD in order to reduce the amount of nitrogen oxide and soot emissions.

What are the key pros and cons of diesel vs. gasoline engines?

They typically deliver 25 to 30 percent better fuel economy than similarly performing gasoline engines

Diesel engines do not need a spark plus or distributors

Higher torque…can start moving faster than a gasoline


cold weather performance can be poor and lead to fuel gelling if left untreated

not as fast as gasoline cars…they lack the zip

More expensive on a gallon basis vs. gasoline in the US

What types of additives are used in diesel fuel? 

The majority of the diesel fuel sold in the US does not contain additives.  The only exception is during the winter time when end users will buy winterized diesel to help protect against fuel gelling.  As engine manufacturers look to improve engine performance (smaller, but hotter engines that operate with higher pressures), there is an increase in the susceptibility to contaminants and deposits.  Additionally, increases in the amount of biodiesel being blended with regular diesel may also impact the overall quality of the blended diesel.  Therefore, additives are likely to play an even stronger role in improving overall diesel fuel quality.  There are four major types of additives used in diesel:

Detergents:  additives that clean and protect against deposits or contaminants from critical engine parts.  In diesel engines, the most significant focus for cleanliness lies in the fuel injector which injects fuel into the combustion chamber prior to combustion.

Cetane Number Improvers (CNI):  Cetane is a measure of diesel combustion quality (analogous to octane for gasoline engines). Cetane improver boosts the cetane number of the fuel, thus increasing the combustion tendency of the fuel, especially when starting a cold diesel engines

Cold Flow Improvers (CFI):  to improve the winter operability characteristics of diesel, cold flow improvers are added to diesel during the late fall to early spring time period.  These additives modify the shape of the wax crystals that are normally found in diesel and prevent them from clumping and settling at lower temperatures.

Demulsifiers:  An emulsion is a mixture of two or more liquids that are normally unmixable, such as water and fuel.  Demulsifier separate emulsions which allows the components to flow through the fuel system and reduce the chance of microbial growth or corrosion from occurring.

There are other types of additives including anti-foaming agents, antioxidants and metal deactivators – all of which have an important role in maintaining diesel fuel quality.