Sylvie Willis
Diesel and gasoline are both refined oils, but diesel is slightly heavier, with a longer and heavier molecule. Diesel is also less volatile, making it harder to ignite. It is classified as combustible, requiring compression and heat to operate. Gasoline, on the other hand, is more flammable and burns quicker and hotter. These differences have implications for their respective uses in vehicles and machinery, with gasoline preferred for lightweight, high-performance cars, and diesel favoured for heavy machinery and vehicles that require more torque, such as trucks and boats.
| Characteristics | Values |
|---|---|
| Density | Diesel: 0.820-0.85 kg/L; Gasoline: 0.70-0.775 kg/L |
| Energy Release | Diesel: 37.7-43.1 MJ/L; Gasoline: 34.9-43.2 MJ/L |
| CO2 Emissions | Diesel: 73.25 g/MJ; Gasoline: 73.38 g/MJ |
| Ease of Refinement | Diesel is generally simpler to refine than gasoline |
| Price | In some countries, diesel may be priced higher than gasoline per gallon or liter |
| Engine Compatibility | Diesel fuel is designed for diesel engines, which differ from gasoline engines |
| Engine Performance | Diesel engines are known for high torque output, durability, and fuel economy |
| Fire Risk | Diesel fuel is less prone to catching fire |
| Volatility | Diesel fuels have fewer distillation recovery temperature requirements than gasoline |
| Viscosity | Diesel has a higher viscosity than gasoline |
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What You'll Learn
Diesel engines are more fuel-efficient
The higher efficiency of diesel engines is mainly due to their higher compression ratio. The internal combustion chamber of a diesel engine is much larger and compresses much further, causing the explosion of the diesel-air mixture. In contrast, a gasoline engine's compression is ignited by a spark at the top of the chamber. This higher compression ratio means that diesel engines need more material to handle the pressure, so the engine is heavier.
The higher torque of diesel engines provides better performance for hauling heavy loads or towing. This makes diesel engines more attractive for heavy equipment and large vehicles like trucks. Diesel engines also tend to be more durable and last longer than petrol engines, with reliable operation and minimal required maintenance.
However, it is important to note that diesel engines have higher purchase prices and maintenance costs due to the complexity of the engines. Additionally, diesel fuel may be priced higher than petrol per gallon or litre in some parts of the world.
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Diesel is denser than gasoline
The higher density of diesel fuel is due to its chemical composition. About 86.1% of diesel fuel mass is carbon, compared to gasoline which has a higher energy density of 46.4 MJ/kg. When burned, diesel offers a net heating value of 43.1 MJ/kg, while gasoline offers 43.2 MJ/kg.
The higher density of diesel also contributes to its higher compression ratio compared to petrol engines. This higher compression ratio results in a longer stroke by the piston, allowing the piston to be pushed against by the diesel combustion for a longer duration. However, the slower burning rate of diesel fuel means that the engine cannot reach high rpm, limiting its maximum speed.
The denser composition of diesel also makes it less prone to catching fire. It is classified as combustible rather than flammable since it requires both compression and heat for ignition. This higher flashpoint of diesel fuel makes it a safer option for fuel storage and transportation, particularly in warmer climates.
Overall, the higher density of diesel fuel compared to gasoline results in greater energy efficiency, improved fuel economy, and enhanced safety characteristics.
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Diesel is harder to ignite
Diesel fuel is harder to ignite than gasoline because it requires higher temperatures to ignite. Diesel engines have a larger internal combustion chamber that compresses more than gasoline engines, causing the explosion of the diesel-air mixture. Gasoline engines, on the other hand, use a spark from a spark plug to ignite the gasoline-air mixture. The flashpoint of diesel fuel is around 62°C, while gasoline has a lower flashpoint of around -40°C. This means that diesel fuel requires higher temperatures to ignite and will not ignite at temperatures below its flashpoint.
The higher flashpoint of diesel fuel also contributes to its slower burning rate compared to gasoline. In a diesel engine, the piston needs to do a longer stroke to take full advantage of the power delivered by the slower-burning fuel. This longer stroke means that the engine cannot reach high rpm, limiting its maximum speed. Gasoline, with its lower flashpoint and boiling point, is more suitable for engines that require higher rpm and faster burning rates.
Additionally, diesel fuel has a higher volumetric energy density than gasoline. The density of EN 590 diesel fuel is defined as 0.820 to 0.845 kg/L at 15°C, about 9.0-13.9% higher than EN 228 gasoline, which has a density of 0.720-0.775 kg/L at the same temperature. This higher energy density means that diesel engines produce more torque, making them suitable for hauling or towing heavy loads.
The higher compression ratio required for diesel engines also contributes to their heavier weight. More material is needed to handle the higher pressure, making the engine heavier. This weight disadvantage is less important in larger vehicles such as trucks and tractors, where the reliability and fuel efficiency of diesel engines are more advantageous.
In summary, diesel fuel is harder to ignite than gasoline due to its higher flashpoint and the need for extreme pressures to ignite. Diesel engines are designed to handle these higher pressures and temperatures, resulting in their reliable and fuel-efficient performance, especially in larger vehicles with heavy loads.
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Diesel produces more torque
Diesel fuel is any liquid fuel specifically designed for use in a diesel engine, a type of internal combustion engine in which fuel ignition occurs without a spark. Instead, the inlet air is compressed, and then the fuel is injected. Diesel engines are used in tractors and heavy equipment, as well as in armoured fighting vehicles and tanks.
Diesel engines produce more torque than gasoline engines. This is due to several factors, including the higher compression ratio in diesel engines, the nature of diesel fuel, stroke length, and cylinder pressure.
Firstly, diesel engines have a higher compression ratio than gasoline engines. This is because diesel engines lack spark plugs, so the piston needs to run to the edge of the cylinder to increase compression and superheat the air-fuel mixture to create combustion. This higher compression leads to a more complete combustion and more torque per combustion event.
Secondly, the nature of diesel fuel itself contributes to higher torque. Diesel fuel has a higher caloric value and is more energy-dense than gasoline. When injected, diesel fuel ignites immediately due to the heat generated by high compression, leading to rapid expansion and high torque. Diesel fuel also has a longer combustion duration, which sustains cylinder pressure.
Thirdly, diesel engines typically have longer strokes than gasoline engines, which increases the distance in the torque equation. The longer stroke, combined with the higher compression ratio, creates more of a moment arm against the crankshaft, resulting in significantly more torque.
Finally, diesel engines have higher cylinder pressure, which, along with the longer stroke, generates more torque. The heavy components necessary to withstand the high compression ratio and cylinder pressure limit engine speed, so the excessive piston speed associated with long strokes is not an issue.
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Diesel is more commonly used in large vehicles
Diesel fuel is commonly used in large vehicles such as trucks, trains, submarines, tractors, barges, and heavy load vehicles. Diesel engines are also used in most construction, farming, and military vehicles. Diesel engines are internal combustion engines that compress air to high pressure to ignite the diesel fuel in the cylinder. Diesel fuel is injected into hot compressed air, where it immediately begins to burn due to the temperature.
There are several reasons why diesel is more commonly used in large vehicles. Firstly, diesel engines offer higher torque, which is necessary for hauling or towing heavy loads. The higher energy density of diesel fuel results in greater torque output, allowing heavy vehicles to move even at slow speeds. Diesel engines also have a higher compression ratio compared to petrol engines, leading to higher efficiency. This higher compression ratio, however, requires a stronger and heavier engine block, making diesel engines better suited for larger vehicles that can accommodate their size and weight.
Another advantage of diesel engines in large vehicles is their slower burning rate compared to petrol engines. This slower burning rate allows the piston to be pushed against by the diesel combustion for a longer duration, resulting in better fuel economy. While this limits the engine's ability to reach high RPM, it is not a concern for large vehicles that do not require high revolutions per minute. Additionally, the slower burning rate of diesel fuel reduces the risk of stalling, making it a safer choice for heavy vehicles.
Diesel fuel also has safety benefits, especially for military vehicles. Diesel fuel is less flammable and less explosive than other fuels, making it a preferred choice for military tanks and trucks. Furthermore, diesel engines are generally more durable and long-lasting due to their construction with larger blocks and thicker materials. Routine maintenance, such as replacing fuel and air filters and radiator care, can help ensure the longevity of diesel engines in heavy vehicles.
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Frequently asked questions
Yes, diesel is a hydrocarbon mixture found on the heavier end of the crude oil spectrum.
Diesel fuel is denser than gasoline, providing more energy per gallon and better fuel economy. It is also less volatile, making it harder to detonate. Diesel engines also produce more torque, making them ideal for hauling heavy loads.
Diesel engines are more expensive to build and heavier due to the higher compression ratio required for detonation. They also have more polluting emissions, although modern diesel engines have significantly reduced sulfur content.
Diesel fuel tends to receive tax breaks as it is used extensively in industries such as trucking, heavy machinery, and buses. However, taxes may vary depending on the location and intended use of the fuel.
No, using the wrong type of fuel in your engine can cause substantial damage. Diesel fuel has a higher energy density and does not require a spark plug for ignition, while gasoline engines have lower torque and require spark plugs.
