When choosing a new vehicle for yourself, there are a few factors you will need to consider. You want to decide whether you want a sedan, SUV, or truck. Then, you have to choose the types of features that you want. Also, you will need to consider whether you want a diesel or gas engine.

However, you might be wondering what is the difference between petrol engine and diesel engine. In this guide, we will go over the differences between the two so you can decide which option is better for you.

History of the Diesel and Petrol Engine

How these two engines differentiate starts with how they were invented. 

Petrol Engine Invented in 1876

The gas engine was invented by Nikolaus August Otto in 1876. However, to power the vehicle, only 10% of the fuel was used and it wasn’t particularly efficient. Most of the fuel simply produced heat. However, the basic blueprint for modern car engines was created with this gas engine.

Diesel Engine Invented in 1892

Rudolf Diesel learned about the poor efficiency of gasoline engines while he was studying to be an engineer at the Polytechnic High School in 1878. He was set on discovering a more efficient solution. The combustion power engine was invented and patented by him in 1892. Nowadays, the combustion power engine is what we call the diesel engine.

What is the Difference Between Petrol Engine and Diesel Engine?

Both diesel and petrol engines are internal combustion engines. What this means is that the fuel is combined with an oxidizer in a small enclosed space, which as a result produces enough energy to power your vehicle.

What are some of the key differences between these two types of engines?

Difference 1: Power Output

You will see many discussions about torque and horsepower when you’re researching options for your new vehicle. Torque is a measurement of the twisting force on the driveline in the engine, while horsepower is used to measure the power.

Torque vs. Horsepower

Your vehicle will be slow to accelerate if it has lots of horsepower but little torque, since torque is what gets the vehicle moving. Diesel engines tend to have less horsepower and higher torque. This is the reason why big trucks usually have diesel engines, and sports cars typically have gasoline engines.  Big trucks need more torque that a diesel engine provides in order to move heavy loads, while sports cars need the horsepower that gasoline engines offer.

Difference 2: Engine Operation

Diesel and gas engines have similar operations in the basic sense. Both use a series of rapid explosions and internal combustion within the engine to propel a vehicle forward by turning fuel into mechanical energy. However, the difference between them is the process through which these explosions happen.

The air is first compressed in a diesel engine, which makes the air hot. Then, the fuel ignites it when it hits the hot air. On the other hand, in a gasoline engine, the fuel mixes with air that is compressed by pistons. The vehicle is moved as a result of the spark plugs that ignite this mixture.

Difference 3: Fuel Injection

Diesel and gasoline engines inject fuel in different ways. 

Gas Engine Fuel Injection

Fuel injection in a gasoline engine can happen two ways: a carburetor or a port injection. A carburetor can mix the air and the fuel together before it sends it into the cylinder to compress. In the other method, a port injection system injects air into the fuel just before the intake stroke.

Diesel Fuel Injection

The fuel is injected directly into the cylinder in a diesel engine. The diesel injectors might become a complicated part of the process since this process is an important part of how diesel engines work. In order for the process to work and to deliver the fine mist of fuel that is necessary, the injectors need to withstand a large amount of pressure and high temperatures. Even today, engineers are trying to make this system more efficient than it is.

Diesel Engine Advancements

Engine advancements examples include glow plugs and engine control modules. A glow plug is a hot wire that can raise the air temperature in a cold engine quickly in order to help it start more efficiently. An engine control module uses several sensors to correctly time the injection.  

Difference 4: Reliability

Diesel engines have fewer parts that can malfunction due to the fact that they function without spark plugs and the electrical system needed to operate the spark plugs. Before they need any type of service, diesel engines can deliver more operation hours and more miles. Also, when something does happen to go wrong, diesel engines are the ones that usually have smaller repair bills.

Difference 5: Efficiency

Besides reliability, another difference between gasoline and diesel engines Is efficiency. When compared to gasoline engines, diesel engines tend to have higher fuel economy numbers. These numbers are a result of the structure of the engines.

A gas engine needs to keep a low compression ration, because it needs to make sure it doesn’t reach a temperature that could cause self-ignition. Since during the intake stroke, a diesel engine doesn’t have fuel in the mixture, it can have a higher compression ratio and compress more air. A better fuel efficiency is reached if there is a higher compression ratio.

Difference 6: Diesel Fuel and Gasoline Fuel

Diesel and gasoline engines require different types of fuel due to the fact they both operate in a different manner. Even though both diesel and gasoline start out as crude oil that is mined from the earth, they are converted into different types of fuels through the refining process. Diesel fuel has more energy density and it is thicker than gasoline, which also means that it evaporates more slowly than gasoline fuel.

Diesel Fuel More Efficient

These features are another thing that contributes to the better fuel economy of diesel engines rather than gas engines. Even though gasoline fuel is less expensive than diesel fuel, typically most diesel engines need less fuel to get the same amount of work done as a gasoline engine.


In addition, owners of a diesel engine have one more fueling option that is available to them, and that is biodiesel. Biodiesel fuel is made from sources that aren’t petroleum, for instance vegetable oil.

In order for a diesel engine to operate on biodiesel, some modifications will need to take place, and this is especially true if you have an older diesel engine. However, sustainability and efficiency are becoming increasingly popular, so this might be the next frequent alternative fuel.

Why Do People Prefer Diesel Cars?

Diesel engines were primarily used in commercial vehicles and large trucks in the past. However, nowadays, many passenger vehicles use this type of engine.

Despite the fact that diesel is more expensive, diesel cars have become more and more popular amongst consumers in the past few years. This might be due to the fact that you get more miles to the gallon and that diesel is a more efficient option.

Having said that, vehicles that have a diesel engine can be more expensive than cars that have a petrol engine, because they require a stronger build, and they are more popular, thus requested on the market. The engine must be heavier due to the fact that the cylinders of a diesel engine are a lot more forceful than in a petrol engine

Advantages of Owning a Diesel Vehicle.

Advantage 1.      Greater Torque

As we previously mentioned, the design of the diesel engine, more specifically its high compression and slow fuel burn, produces greater torque than other types of engines. 

Torque is just as important as horsepower and it relates to the ability to accelerate and pull loads. This extra torque is the reason why semis and large trucks use diesel engines.

Advantage 2. Lower Fire Hazard

Since diesel fuel has a higher flashpoint than gasoline, the chance of a fuel igniting if an accident happens is lower. If it’s under extended direct heat, of course it can catch fire. But, if we’re talking about a quick little spark, then it would be less likely to ignite.

Advantage 3. Lower Maintenance

Gasoline engines and diesel power plants work very differently from one another. Diesel power plants have an increased lifespan and reduced maintenance. The main difference is that in order to ignite the fuel they use hot compressed air, and they lack a spark ignition system. 

The absence of this system produces a very reliable engine, and reduces the number of potential electrical failures, and reduces maintenance costs. You also extend the time between the maintenance services that are required for your engine to work in a proper manner.

Advantage 4. Lower Taxes

Road tax laws have changed as a result of carbon dioxide emissions, and diesel engines tend to have lower taxes when compared to vehicles that have a gasoline engine.

Advantage 5. Better Fuel Economy

As mentioned, diesel engines generate more power from less fuel as a result of their higher compression rating and are more fuel efficient when compared to vehicles that have a gasoline engine. It is possible to get even better fuel economy with the addition of modern fuel-injection high-pressure systems. What’s even better, the fuel economy and output can be pushed even higher with a turbocharger.

Drawbacks to Having a Diesel Vehicle

Even though the diesel engine is the more popular option on the market right now, there are some drawbacks to it, and we would like to mention them so you can decide whether a diesel engine is the right choice for you. Some of the potential drawbacks that diesel engines have are the following:

Drawback 1. Weaker Performance in Cold Climates

Diesel engines have a tendency to gel up during cold weather. In order to combat this, many people who own diesel engines keep their vehicle running when the weather is colder, or they have an engine block heater installer. Your diesel car will be more fuel efficient if you live in a warm area where cold weather isn’t a problem.

Drawback 2. Higher Entry Fee

Usually, a turbo diesel vehicle will cost you more money up front. This is not a result of any additional costs to develop the technology or engine, but instead, it’s a result of the supply and demand chain. You will find out that a diesel vehicle will cost you several thousand dollars more than a vehicle that has a standard gasoline engine and is similarly equipped as the diesel vehicle.

Drawback 3. Higher Cost for Diesel Fuel

When driving a diesel car, you won’t need to fill up your tank as often as you would with a gasoline engine, but you will need to pay more for the fuel once you need to put gas in. The international demand for diesel is also very high, which pushes up the cost of the fuel as well.

Final Thoughts

In order to make your final decision, you will need to consider your driving needs. A diesel engine would be ideal for you if you do a lot of highway driving and you know that you’ll cover a lot of miles. A petrol car with a smaller engine might be more appropriate if you’re not so certain that you’ll be covering many miles and you will only be driving your car locally. Now that you know the differences between these types of engines, you should have an easier time picking one out.