By Jack Busch, Updated Aug 30, 2022
Diesel is noticeably denser and oilier than gasoline, with a distinct odor. At fueling stations, diesel pumps are clearly labeled and the fuel is stored in yellow containers, whereas gasoline uses red and kerosene uses blue. On a molecular level, gasoline typically consists of C9H20, while diesel is richer, around C14H30.
As a fossil fuel, diesel is extracted from crude oil through fractional distillation. Crude oil is mined deep underground and, according to a 2005 Organic Chemistry article by Keith A. Kvenvolden, originates from ancient plant and animal biomass subjected to high heat and pressure.
Diesel engines rely on internal combustion. Air enters the cylinder via the intake valve, is compressed by the piston, and fuel is injected. The compression heats the air, igniting the fuel and driving the piston back down. This four‑stroke cycle powers the engine.
Unlike gasoline engines, which mix air and fuel before combustion and use a spark plug, diesel engines depend solely on compression ignition. This fundamental distinction gives diesel engines higher thermal efficiency and torque.
Diesel typically contains fewer additives than gasoline, reducing greenhouse‑gas emissions. However, combustion releases more sulfur, contributing to acid rain. Balancing these factors is key to evaluating diesel’s environmental footprint.
Biodiesel, derived from vegetable oil, is a renewable alternative that burns cleaner than petroleum diesel. It can be blended with conventional diesel (e.g., B20, a 20 % biodiesel mix) or used at full strength (B100). While biodiesel offers environmental benefits, it can dissolve deposits in fuel lines, so filters need frequent replacement.
