What is the Difference Between Gasoline, Diesel Fuel, and Fuel Oil?

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  • Written By: R. Anacan
  • Edited By: Bronwyn Harris
  • Last Modified Date: 14 May 2020
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Gasoline, diesel fuel and fuel oil are all petroleum products. Petroleum is a mixture found in the earth, composed of crude oil and natural gas. While the products that are derived from petroleum power the modern world, raw petroleum is of little use until it is refined. It is the refining process that converts crude oil into gasoline, fuel oil, and diesel fuel.

Crude oil is a complex mixture of hydrocarbons that are chained together in different lengths. These chains have different characteristics and properties and form the basis for the individual products created out of raw petroleum. To be able to convert these hydrocarbon chains into gasoline, diesel fuel, fuel oil and other petroleum products, they have to be separated from other chains.

Crude oil is separated into these different chains through distillation. During distillation, crude oil is heated in a distillation column. Collection trays are placed at differing heights in the column. As the crude oil is heated, the vapors formed through the boiling process rise up the column. The lighter chains take longer to condense and collect in the trays towards the top and the heavier chains condense more quickly and collect in the trays towards the middle and bottom of the distillation column. Once they have been separated, they are treated further through various processes to create the different petroleum products.

Gasoline is formed from shorter and lighter chains of hydrocarbons than either diesel or fuel oil. Gasoline is lightweight, extremely volatile and evaporates quickly. These qualities contribute to gasoline powered engines having more horsepower and acceleration than an equivalent diesel engine. However, gasoline is not as efficient a fuel as diesel or fuel oil. Gasoline produces approximately 124,000 British Thermal Units (BTUs) of energy per gallon (3.79 liters) while a diesel engine produces approximately 139,000 BTUs of energy per gallon (3.79 liters).

Diesel is a middle weight product that is heavier than gasoline. It has the appearance of oil and is often referred to as diesel oil. It does not evaporate as quickly nor is it as volatile as gasoline. It takes less refining from crude oil to make diesel fuel, which often makes diesel less expensive than gasoline. The increased mileage and lower cost make diesel a popular choice of fuel in many parts of the world.

Fuel oil used for the heating of homes is slightly heavier than diesel fuel but shares similar properties and is considered a middle distillate as diesel is. Fuel oil for residential use produces approximately the same amount of BTUs as diesel and has a low volatility which makes it ideal for residential heating. Fuel oil that is used in large industrial applications such as electric power generators are considered residual fuel oils and are heavier than gasoline, diesel fuel, and home heating oil.

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Post 7

Can I use fuel oil in my diesel engine car?

Post 3

Really enjoyed this article. Thank you for the information.

Post 2

@ Amphibious54 - You bring up a good point about cracking. Most hydrocarbon chains can be cracked to create different hydrocarbon chains. This allows refineries to create more optimal ratios of different products from the crude they use. A refinery may not need as much coke, but needs more gasoline so they can use different techniques to re-arrange, break or combine different hydrocarbon chains.

The alkylation process uses catalysts to re-arrange chains of hydrocarbons into high octane chains which are mixed with gas to create the different octane ratings. Unification combines hydrocarbon chains in a reformer to create aromatics (used to make chemicals and plastics), and hydrogen gas.

These are only a few examples of the different refining techniques, but the versatility of hydrocarbons is what makes petroleum so valuable. It can be used to make anything from plastics and natural gas, to fuel oils, to the coke that is used in the metal smelting industry.

Post 1

Diesel actually takes more refining than gasoline before it is ready for the U.S market because the sulfur content in the diesel has to be lowered during the post distillation phase of refining. While the article is right that gasoline requires more refining within the distillation process, this is only because refineries try to produce more gasoline than any other petroleum product so chemical cracking is necessary to increase the gasoline yields of crude.

The gasoline cracking is less costly than the diesel post distillation refining process; ultimately making diesel cheaper than gasoline. If U.S. energy regulations did not require cars to run on low sulfur clean diesel than it surely would cost less than gasoline; especially when the extra expense of adding ethanol to gas for oxygenation is taken into account.

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