What is the Difference Between Heating Oil and Diesel

The main difference between heating oil and diesel is that heating oil generally has a higher sulfur content compared to diesel.

Heating oil and diesel are two related but distinct petroleum products commonly used as fuels. Despite their similarities in composition and appearance, these fuels have different additives and applications.

Key Areas Covered

1. What is Heating Oil  
      – Definition, Features 
2. What is Diesel
      – Definition, Features, Applications 
3. Similarities Between Heating Oil and Diesel
      – Outline of Common Features
4. Difference Between Heating Oil and Diesel
      – Comparison of Key Differences
5. FAQ: Heating Oil and Diesel
      – Frequently Asked Questions

Key Terms

Heating Oil, Diesel

Difference Between Heating Oil and Diesel - Comparison Summary

What is Heating Oil

Heating oil, often referred to as fuel oil, is a crucial component in residential and industrial heating systems. Its chemical composition primarily comprises hydrocarbons, derived from crude oil through a refining process. The two main types of heating oil are #1 fuel oil (kerosene) and #2 fuel oil, with the latter being more commonly used for heating purposes.

The #2 fuel oil consists of long-chain hydrocarbons, predominantly alkanes, which are saturated hydrocarbons. These molecules contain carbon and hydrogen atoms arranged in a linear or branched structure. The combustion of heating oil involves breaking these hydrocarbons into simpler compounds, such as carbon dioxide and water vapor, releasing energy in the form of heat.

Differentiate Heating Oil and Diesel

During the heating process, heating oil undergoes combustion, a chemical reaction with oxygen from the air. This reaction is exothermic, meaning it releases heat energy. The general equation for the combustion of hydrocarbons in heating oil can be represented as follows:

Fuel Oil(hydrocarbon) + Oxygen → Carbon Dioxide + Water Vapor + Heat Energy

Incomplete combustion, often undesirable, can lead to the formation of carbon monoxide (CO) and other harmful byproducts. Proper ventilation and maintenance of heating systems are essential to ensure complete combustion and minimize the production of pollutants.

Additionally, the efficiency of heating oil combustion is influenced by factors such as burner design, temperature control, and the overall condition of the heating equipment.

Advancements in technology have led to the development of cleaner-burning heating oil formulations and more efficient combustion systems, addressing environmental concerns and improving overall energy efficiency.

What is Diesel

Diesel fuel, a hydrocarbon-based liquid, plays a crucial role in powering internal combustion engines, particularly in the transportation and industrial sectors. The chemistry of diesel involves a complex composition of hydrocarbons, typically alkanes, which are saturated hydrocarbons containing only single bonds between carbon atoms. The primary source of diesel is crude oil, and its composition varies based on the crude oil’s origin and refining processes.

Diesel fuel primarily consists of molecules with carbon chain lengths ranging from 8 to 21 carbon atoms. The most common types are C10 to C15 alkanes. These long carbon chains contribute to the higher energy density of diesel compared to gasoline, making it an efficient fuel for heavy-duty vehicles and machinery. The absence of double bonds in alkanes provides stability to the molecules, reducing the risk of premature ignition, a characteristic known as the cetane number.

Heating Oil vs Diesel

During combustion, diesel undergoes a multi-step process. First, the fuel vaporizes and mixes with air in the combustion chamber. Then, under high temperature and pressure, the diesel-air mixture ignites. The heat generated during combustion causes the expansion of gases, leading to the movement of pistons and ultimately powering the engine.

Diesel combustion releases various byproducts, including carbon dioxide (CO2), water vapor, nitrogen oxides (NOx), and particulate matter. Diesel engines strive for an optimal balance between complete combustion for efficiency and minimizing emissions for environmental considerations. Advancements in diesel engine technology, such as direct injection and exhaust after-treatment systems, aim to enhance combustion efficiency and reduce pollutants.

Similarities Between Heating Oil and Diesel

  • Heating oil and diesel are similar in composition, both being distillates of crude oil.
  • They typically have a similar appearance, often being light to dark amber in color.
  • They have comparable densities.

Difference Between Heating Oil and Diesel


Heating oil is a refined petroleum product used primarily for residential and commercial heating systems, whereas diesel is a type of fuel derived from crude oil through a refining process.

Sulfur Content

Heating oil generally has a higher sulfur content compared to diesel.


Diesel used in vehicles may contain additives, such as lubricity improvers and cetane boosters, to enhance engine performance. Heating oil, being used in stationary equipment, might lack some of these additives.


Diesel is primarily designed for use in internal combustion engines of vehicles and is subject to strict regulations to meet emission standards. Heating oil is used for heating systems and is subject to different regulatory standards, often with a focus on safety and efficiency in stationary applications.

FAQ: Heating Oil and Diesel

Is heating oil the same as diesel?

No, heating oil and diesel are not the same.

Can heating oil be used in diesel engines?

Diesel engines are designed to run on diesel, not heating oil.

Can you mix diesel oil with heating oil?

Yes, you can mix diesel oil with heating oil.


Heating oil and diesel are two related but distinct petroleum products commonly used as fuels. The main difference between heating oil and diesel is that heating oil generally has a higher sulfur content compared to diesel.


1. “Heating Oil.” Wikipedia. Wikipedia Foundation. 
2. “Diesel Fuel.” Wikipedia. Wikipedia Foundation. 

Image Courtesy:

1. “COP 23 – heating oil for tent city” By Spielvogel – Own work (CC BY-SA 4.0) via Commons Wikimedia
2. “Red Diesel Tank” By Meena Kadri (CC BY 2.0) via Commons Wikimedia

About the Author: Hasini A

Hasini is a graduate of Applied Science with a strong background in forestry, environmental science, chemistry, and management science. She is an amateur photographer with a keen interest in exploring the wonders of nature and science.

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