As a domain expert in the field of automotive engineering, I can provide a comprehensive explanation of why diesel engines are more efficient than gasoline engines. The efficiency of an engine is typically measured by its thermal efficiency, which is the ratio of the work done by the engine to the heat energy released by the complete combustion of the fuel.

**Diesel engines are inherently more efficient** due to several key factors:


1. Higher Compression Ratio: Diesel engines operate at a higher compression ratio compared to gasoline engines. This means that the air-fuel mixture is compressed to a greater extent before ignition, leading to a more complete combustion process and thus higher energy conversion efficiency.


2. Compression Ignition: Unlike gasoline engines, which use spark plugs to ignite the air-fuel mixture, diesel engines use compression ignition. The high pressure and temperature from the compression process cause the diesel fuel to ignite spontaneously when it is injected into the combustion chamber. This results in a more efficient and cleaner burn.


3. Lubrication and Detonation: Diesel fuel has a higher lubricity than gasoline, which helps reduce friction and wear within the engine. Additionally, diesel engines are less prone to detonation (or knocking) due to the slower combustion process, allowing for higher compression ratios and more efficient energy conversion.


4. Higher Energy Content: Diesel fuel has a higher energy content per unit volume than gasoline. This means that for the same volume of fuel, a diesel engine can produce more work, contributing to its higher efficiency.


5. Turbocharging: Many modern diesel engines are turbocharged, which allows them to draw in more air and thus burn more fuel, increasing power output and efficiency.


6. Heat Management: Diesel engines are typically better at managing heat. They can operate at higher temperatures without the risk of knocking, which allows for more efficient energy conversion.

7.
Economical Cruising Speeds: Diesel engines are often designed to operate most efficiently at lower RPMs, which is beneficial for long-haul driving where maintaining a constant speed is common.

8.
Long-term Durability: Diesel engines are known for their durability and longevity. The absence of spark plugs and the robust nature of diesel engines contribute to their long service life, which can indirectly contribute to overall efficiency by reducing maintenance and replacement costs.

The statement that "vehicles powered by compression-ignition engines are often dramatically more fuel efficient than their gasoline counterparts" is indeed correct. The efficiency advantage can be as much as 30 percent, which is a significant difference. For example, a vehicle with a 3.0-liter turbo diesel engine might achieve better fuel economy than a similarly sized gasoline engine, as the diesel engine can convert more of the fuel's energy into work.

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In fact vehicles powered by compression-ignition engines are often dramatically more fuel efficient than their gasoline counterparts. In fact they can be up to 30 percent thriftier, which is HUGE. ... But an identical model that's motivated by a 3.0-liter turbo diesel engine clocks in at 28.Sep 18, 2014read more >>