The Differences Between A Diesel & Gasoline Engine?

Diesel was not as common in everyday vehicles as they are now. Many of us, myself included, had the perception that diesel engines were only for big semi trucks that pollute our environment and take up way  too much room on the highway.

However, Diesel engines have been growing in popularity among everyday cars, especially if you want to buy a European car. Outside the United States, diesel engines account for almost 50% of all the cars on the road today. This may be the reason why we see the growing trend here in America. Though we are slow to adopt the diesel engine, we are quickly seeing the benefits of having a diesel engine.

Thanks to Mercedes and other auto companies, Diesel engines are becoming less pollutant, more efficient, and better at fuel economy than gasoline engines. With the increase in advantages, the public still understands so little about how diesel engines actually work. What makes then more efficient? How do they get better fuel economy? Why does diesel fuel cost more?

Let’s walk through a few points on how Diesel engines are different than gasoline engines and the possible advantages.

Spark Plugs


Both Diesel engines and Gasoline engines work off of combustion. The cylinders in the engine compress the air so much that it gets hot. In gasoline engines, fuel injectors then inject fuel into the cylinder and a spark plug ignites the fuel. The pressure from the compressed air and ignited fuel causes a small explosion to force the cylinder back down. This process happens several times per second.

With diesel engines, there are no spark plugs to ignite the fuel. Diesel engines compress the air so much that when fuel is injected into the cylinder, it ignites from the heat. Many people believe this type of combustion process is more reliable because you are relying more on the chemistry of your engine rather than the mechanics. Especially with spark plugs that have to be changed every so often, many diesel drivers appreciate the fact that they do not have to deal with this extra maintenance.

Fuel Power


We know that gasoline fuel and diesel fuel are different. That’s why we always see a separate gas nozzle for diesel fuel at gas stations. This different between the two types of fuels is the concentration. Gasoline is like syrup and Diesel is like honey. Diesel holds more potential energy to keep your engine running which means less fuel is needed for combustion. This is why you tend to see diesel engines having 30+ MPG. Whether this is an advantage or not depends on fuel prices. Since diesel costs more than regular gasoline, it sometimes balances out the advantages of having better fuel economy.


One of the main reasons why semis use diesel engines is because of a diesel engines ability to have high amounts of torque. This is not the same as horsepower which deals more with speed. Torque is what is used more for hauling heavy weight by adding more power to the drivetrain which makes the wheels spin. For many car owners, the difference between torque and horsepower doesn’t matter. When accelerating at a stop light or passing a slow driver, both torque and horsepower can accelerate the car quickly. The difference is when you start weighing the car down. If you have a SUV packed full of six grown adults, torque may help you accelerate faster at the light than horsepower.

If more power is your thing, then look at turbo-diesels commonly found in Audi, BMW, Mercedes, VW, and Porsche.

Because diesel engines have higher torque and create a stronger internal combustion, diesel engines have to be built stronger than gasoline engines. It is a continuing debate among diesel car owners versus gasoline engines as to which engines last longer. Many diesel engines have been known to last more than 300,000 miles.

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Written by Spotlight Automotive