Why Do Diesel Engines Last Longer?

Most of the industries, including marine, agriculture, military, construction, and transport, rely on diesel engines. Diesel engines are known to provide enormous torque, which is very helpful for moving heavy cargo. They are extremely efficient when subjected to load and can last 2-4 times longer than an engine fired by gasoline.

This is why they are considered to be the most durable as well as reliable mechanical creations. Some of the most innovative motorized vehicles use diesel engines due to this very reason. You may wonder why these diesel engines last longer when compared to other engines. Well, you can find out about this in-depth by reading this article.

What is a Diesel Engine and How Does it Work?

Diesel engine is an internal combustion engine commonly used in machinery, motorized vehicles, and power generators. Invented in the 19th century, it is named after its inventor, Rudolf Diesel.

It works on the principle of compression ignition, where the heat of compression is used to ignite the air-fuel mixture. This is different from gasoline engines, where a spark plug is used to ignite the air-fuel mixture. You can better understand a diesel engine’s workings from the steps below.

• Intake Stroke: The piston in the engine moves down to create a vacuum in the cylinder. Once the intake valve opens, the fresh air gets drawn inside the cylinder.
  
• Compression Stroke: The engine piston moves upward, compressing the air inside the cylinder. This increases the temperature significantly.
• Fuel Injection: Fuel injection occurs inside the cylinder near the compression stroke’s end. The fuel injector atomizes the fuel into tiny droplets, which then gets mixed with the air at high temperature.
• Combustion: Due to the high temperature and pressure inside the cylinder, ignition occurs when fuel droplets get mixed with the hot air.
• Power Stroke: When the piston moves down, it is called the power stroke. In this phase, the energy of combustion is converted to mechanical motions. Since the piston is directly connected to the crankshaft, the moment it moves down, it rotates. This transfers power to the vehicle’s wheels.
• Exhaust Stroke: At the end of power stroke, the piston moves up again. This motion causes the exhaust gasses to get expelled from the cylinder. At this stage, the exhaust valve opens, pushing the gasses to the exhaust system.
• Repeat: As long as both fuel and air are available, the machine’s engine keeps repeating this 4-stroke cycle of intake, compression, power, and finally exhaust.
  

Reasons For Diesel Engines Lasting Longer Than Gas Engines

Here are a few reasons diesel engines last longer than gas engines.

1. Design of Diesel Engine

Compared to gas engines, diesel engines have a high compression ratio and cylinder pressure. Since the diesel engines have a larger camshaft and crankshaft, they are equipped with larger and sturdier bolts and bearings. This would mean that they have increased clearance, so the oil flow is much better. Since even the engine lubrication is better, engine wear is significantly less, improving engine longevity. A few other things which improve engine longevity in a diesel engine are,

• Piston cooling jet in a diesel engine sprays the engine oil at the piston’s bottom area. This ensures proper piston lubrication, reduces friction, keeps the piston cool, and prevents premature wear.
• Gear-driven design in the diesel engine ensures minimal timing belt failures. This would help you save maintenance money.
• The absence of spark plugs in diesel engines results in a slow fuel burn. This means that the stress will be less while the torque will be more, improving the engine’s efficiency.

2. Diesel Fuel

Diesel engines and gas engines are also different when it comes to the fuel they use. The fuel used in diesel engines is a type of distillate fuel derived from crude oil. Such a fuel causes slower cylinder wear resulting in an increased overall lifespan of the engine. Gasoline is made using aromatic hydrocarbons and behaves just like the corrosive and harsh solvents. Since there is no lubrication here, there is a chance that your engine’s components get excessively worn out. A few other parameters which distinguish diesel fuel from gasoline are,

• Diesel fuel also has a greater BTU of 139,000 than gasoline’s 115,000 BTU. According to the law of thermodynamics, exhaust gasses get cooled faster in diesel engines.
• The initial flame front is also much cooler since the auto-ignition temperature of diesel fuel is 410 ℉, and that of gasoline is 495 ℉.
• Diesel engines run at an air-to-fuel ratio of 25:1 – 70:1, while gasoline engines run at a 12:1 – 16:1 air-to-fuel ratio. The leaner air-to-fuel ratio of diesel engines helps faster EGT’s cooling.
• Diesel fuel also burns slower when compared to gasoline. During combustion in diesel engines, the flame’s laminar speed is pretty slow which ensures the rotating assembly is subjected to minimal shock. This further enhances the durability of the engine.

3. Lower RPMS

Another contributing factor to diesel’s longevity is its operating efficiency. Diesel engines have a lower RPMS and high level of torque when compared to gasoline engines. Since it operates at a lower RPMS, the same power can be achieved with less wear to the rings, pistons, valves, bearings, guides, and cylinder walls. This improves the durability of the engines greatly. Typically, diesel engines are left running when they are not in use for short durations. This is because the initial startup of a diesel engine causes more wear. A constant diesel engine running ensures minimum wear and low heat cycles since the temperature is maintained.

4. Applications

As discussed in the section above, a gasoline engine carries out roughly twice the number of revolutions every minute than a diesel engine. This causes more wear of the internal components of the engine. Almost 75% of engine wear is caused due to the engine heating up. Diesel engines avoid this wear to the components by starting only once or twice a day. For instance, semi-trucks go for even 300 miles without powering down. However, gasoline engine-powered cars are started multiple times each day and every time it is started it typically travels up to 10 miles before it is started up again. This results in more heating and cooling cycles and, ultimately, more wear to the engine’s components.

What is the Life Expectancy of a Diesel Engine?

If you are considering buying a car with improved sturdiness, reliability, and durability, diesel engine-powered cars can be a good option. Gasoline engines can run for about 250,000 to 300,000 miles, after which they might either need a major overhaul or you might need to consider investing in a new car. On the contrary, diesel engines can run for 1,500,000 miles and sometimes even more before its performance starts getting affected. From this, we can conclude that, if maintained well, a diesel engine can run for more than 30 years without any major issues. This is also dependent on external factors and your driving style.

Diesel Engine – FAQs

Conclusion

Diesel engines can last longer than gasoline engines due to the abovementioned factors. Their fuel efficiency, robust design, durability, torque advantage, effective lubrication and exhaust systems make them suitable for heavy-duty applications. Their simple design, which requires minimum maintenance, gives them excellent longevity. When you adhere to the manufacturer’s guidelines to maintain a diesel engine, you can reap its maximum benefits for an extended period of time.