How Does a Diesel Engine Work?

  • 2019 Ford Super Duty Performance

    How Does a Diesel Engine Work?

    If you’re wondering “How does a diesel motor work?” then you’ve come to the right place! The team at Don Johnson Motors have experience with an extraordinary variety of vehicles and heavy-duty machines, and we’re happy to pass along our knowledge to curious friends and neighbors. Once you’ve got the answer, you’ll be well-prepared to select a superior vehicle for your drives around northwest Wisconsin!

Gasoline Engines

Diesel Engines

Compression Ratio

Less efficient


More efficient

Spark Plugs

Internal Combustion

Engine Type

Internal Combustion

Internal Combustion Engines: Know the Basics

If you want to understand how a diesel engine works, you’ll need to have a grasp of the basic mechanics which define internal combustion engines. Both gasoline-powered engines and diesel engines have the following characteristics:

  • Unlike an external combustion engine, where energy is produced before it is routed to the engine, an ICE transforms fuel into power within its primary components: its cylinders.
  • After fuel and oxygen have been taken into the internal combustion engine’s cylinders, heat is required in order to ignite the fuel and generate force.
  • How does transformation take place? In most engines, the downward motion of the piston draws air into the cylinder, and the upward commotion compresses it, triggering ignition by one of a few methods.
2019 Ram 3500 Diesel Engine

Diesel vs. Gas Engines

For many drivers, the easiest way to conceptualize a diesel engine is by comparing it to the more familiar gas-powered engine. Although both are internal combustion engines, there are a few key distinctions to be aware of:

  • An engine that’s driven by gasoline generally compresses air to be 10 times denser than regular atmospheric pressure, meaning it has 10:1 compression ratio. A diesel engine goes even further, compressing air to be 15-25 times denser than it is in the open atmosphere, meaning it has a 1.5x-2.5x higher compression ratio than that of a gas engine.
  • Since the air in a diesel engine’s cylinders is so compressed, it often gets much hotter than the air in a gasoline-powered engine.
  • For this reason, the answer to the question, “Do diesel engines have spark plugs?” is almost always no. Since the air in a diesel engine’s cylinders is so hot, the injection of fuel alone is enough to ignite the chamber.
  • The simplicity of the diesel engine’s design (i.e. the absence of spark plugs) is one of the factors that make it up to 40% more efficient than a comparable non-diesel engine. The other factor is the diesel engine’s lower relative temperature, meaning that less energy is being exhausted as heat.
2019 Chevy Silverado 3500 Diesel Engine

Find Your Diesel Truck at Don Johnson Motors!

At least in the United States, drivers who want to know how a diesel engine works are often on the hunt for the perfect new truck! Compare the pros and cons of gas vs. diesel trucks with Don Johnson Motors.If you’ve already made your decision, check out our list of the best diesel trucks, or start exploring our new diesel truck inventory right away! No matter which model you choose, we can’t wait for you to schedule a test drive.

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(715) 475-1473

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734 West Avenue • Rice Lake, WI 54868

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Don Johnson Motors
Don Johnson Motors
734 West Avenue
Rice Lake, WI, 54868 US
(715) 475-1473
Don Johnson Motors 45.5080292, -91.7657192.