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Why Diesel Engine Cars Give Better Mileage Than Petrol Cars?
Diesel engine cars offer better mileage than petrol engine cars, but have you ever wondered why? Consistent fuel refilling makes a hole in every budget-conscious person’s pocket, so here are the key reasons and mechanisms that result in the better mileage of diesel engine cars.
Diesel cars are often known for delivering better mileage than petrol cars, especially on highways and long-distance drives. This difference is mainly due to the way diesel engines work and the nature of diesel fuel itself.
Higher Energy Content
One of the main reasons diesel cars offer better mileage is the higher energy content of diesel fuel. Diesel contains more energy per litre than petrol. This means a diesel engine can travel a longer distance using the same amount of fuel, which directly improves fuel efficiency.
Higher Compression Ratio
Diesel engines operate at a much higher compression ratio than petrol engines. While petrol engines typically use a compression ratio of around 8:1 to 12:1, diesel engines can go as high as 20:1 or more. Higher compression allows the fuel to burn more completely and efficiently, producing more power from each drop of fuel.
Better Combustion
Unlike petrol engines, diesel engines do not use spark plugs. Instead, air is compressed until it becomes hot enough to ignite the diesel fuel on its own. This process, called compression ignition, results in a more controlled and efficient burn, reducing fuel wastage.
Strong Low-End Torque
Diesel engines generate higher torque at lower engine speeds compared to petrol engines. This means the car does not need to rev as high to move or maintain speed. Lower engine revs result in lower fuel consumption, especially during highway cruising and when carrying heavy loads.
Leaner Air-Fuel Mixture
Diesel engines usually run on a leaner air-fuel mixture than petrol engines. More air and less fuel are used during combustion, which improves mileage. On the other hand, petrol engines require a more precise air-fuel ratio, which limits efficiency.
Better Performance on Long Drives
Diesel engines are particularly efficient on long journeys and highways. They maintain steady speeds with lower fuel usage, which is why diesel vehicles are often preferred for commercial use, taxis, and long-distance travel.
Although modern petrol engines have become more efficient due to technologies like turbocharging and direct injection, diesel engines still maintain an advantage in real-world fuel economy. However, stricter emission norms and rising diesel prices are gradually narrowing this gap.
In simple terms, diesel cars give better mileage because diesel fuel carries more energy, burns more efficiently, and works best at lower engine speeds.