What are the differences between diesel and gasoline?

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The main differences between diesel and gasoline lie in volatility, air mixing capability, energy content, combustion method, emission characteristics, price, odor, energy, and color. The specific details are as follows: Volatility: Gasoline is highly volatile, while diesel is not. Air mixing capability: Gasoline mixes easily with air due to its high volatility, which is why gasoline engines use technologies like direct injection and stratified injection to optimize the air-fuel mixture for more complete combustion. Diesel, on the other hand, does not mix as easily with air, leading to incomplete combustion in diesel engines. This results in unburned components being emitted as black carbon particles, which is why diesel vehicles often produce black smoke and have a strong odor. Energy content: Gasoline consists of smaller molecules with hydrocarbon compounds containing about 8-10 carbon atoms, whereas diesel contains 12-15 carbon atoms. When burned, more carbon atoms release greater energy if combustion is complete. Compared to the same volume of gasoline, diesel provides higher energy, making diesel engines more fuel-efficient under similar thermal efficiency conditions. Combustion method: Gasoline engines use spark plugs for ignition, while diesel engines rely on compression ignition. Gasoline molecules are smaller, more active, and have a lower ignition point. Gasoline engines mix air at an ideal ratio and compress it to around 10 times before igniting with a spark plug. Diesel, with its higher carbon content, requires more air and is harder to ignite with a spark plug. Therefore, diesel engines use a compression ratio of 15-18 to compress the diesel-air mixture (compression raises temperature) until it ignites. Emission characteristics: Gasoline burns at high temperatures, and incomplete combustion leads to partial dissociation of compounds, emitting mainly carbon monoxide, hydrocarbons, and nitrogen oxides. Diesel engines have more air but poorer mixing, leading to carbon soot in oxygen-deficient areas. Due to the excess air, diesel engines emit less carbon monoxide and hydrocarbons but produce more particulate matter and nitrogen oxides. Price: Gasoline is more expensive, while diesel is cheaper. Diesel has higher energy content. Diesel does not require a spark plug and self-ignites under high pressure, making it more efficient but heavier and noisier. Gasoline requires ignition, so gasoline engines are smaller and quieter. Odor: Gasoline has a pungent smell, while diesel has a milder odor. Color: Gasoline is lighter in color, while diesel is darker. Additionally, diesel is mainly used in trucks. Diesel engines rely on compression ignition with a high compression ratio (up to 15), resulting in longer cylinder strokes and higher torque, providing better acceleration. Diesel engines operate at lower RPMs, so their power output is generally lower than gasoline engines, resulting in slower speeds. Gasoline is primarily used in passenger cars. Gasoline engines use spark ignition with lower compression ratios, typically 8-11 for naturally aspirated engines and not exceeding 14 for turbocharged ones.