Explaining the Difference Between Diesel and Gas Engines

They’ve both got unique benefits, but which engine is right for you?

Co-authored by Duston Maynes and Devin McSween

Last Updated: February 4, 2023 References

Differences Between Diesel and Gas Engines

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Benefits of Diesel Engines

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Benefits of Gas Engines

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Which type of engine is better?

Car shopping is so exciting: it's all about finding a make, model, and style that perfectly compliments you. But when it comes to choosing a diesel or gas engine, is there really much of a difference? You might think that the type of fuel you use is the only distinction, but there are actually a lot of differences in their power, energy efficiency, and longevity. Whether you’re in the market for a new car or are simply interested in how diesel and gas vehicles stack up, we’ll tell you all about how they differ. And to help you make the decision that's best for you, we’ll go over the benefits of owning each type.

Things You Should Know

Diesel engines usually have greater fuel efficiency and longevity, but are more expensive than gas engines.
Diesel vehicles are usually the best option if you pull heavy loads and drive long distances.
Gas vehicles are often better to choose if you want a faster, high performing car and don’t drive long distances.

Section 1 of 4:

Differences Between Diesel and Gas Engines

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Diesel engines don’t use a spark plug to ignite while gas engines do. Both gas and diesel engines are combustion engines that go through the same cycle: intake, compression, ignition, and exhaust. On intake, a diesel engine’s cylinders only let in air. This allows the cylinders to compress more powerfully and at a higher rate. When fuel is injected into them during the ignition phase, the heat and pressure is enough to ignite the engine.^{[1]
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- Gas engine cylinders let in both air and fuel at intake. This means they can’t compress as powerfully as diesel cylinders, so they need a spark of electricity from a spark plug to ignite the engine.
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Diesel engines generally have a higher fuel efficiency than gas engines. As it turns out, diesel fuel is actually thicker and more energy-dense than gasoline. So, less fuel is needed to adequately power a diesel engine compared to a gas engine. Combined with the fact that the higher cylinder compression rate allows diesel engines to use the fuel more efficiently, diesel engines typically get more miles to the gallon (kilometers per liter) than gas engines.^{[2]
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- In fact, diesel vehicles tend to be about 20-35% more efficient than gas vehicles. They often get about 6 to 10 more miles per gallon (2-4 kilometers per liter).^{[3]
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Diesel engines usually last longer than gas engines. The higher compression rate of diesel engines usually means that their engines are built more sturdily to better withstand the pressure. The thickness of diesel fuel also makes it a better lubricant for the engine than gasoline. This means that a diesel engine tends to run more smoothly and for longer compared to a gas engine.^{[4]
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- Diesel engines and vehicles often last about 2 times as long as gas engines and cars. Gas engines typically start showing signs of wear and tear around the 100,000 mile (161,000 km) mark, while diesel engines usually need to hit 200,000 mile (322,000 km) mark.^{[5]
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- The greater longevity of diesel engines also tends to give them higher resale values than gas engines.
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Diesel vehicles and fuel are usually more expensive than gas. While diesel engines have great fuel efficiency and longevity, that comes at a price. When buying a new car, diesel models often cost between $3,000 to $10,000 more than the same model with a gas engine.^{[6]
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Research source} Fuel prices constantly fluctuate, but gasoline is also usually at least several cents cheaper than diesel.^{[7]
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- If you're in the United States, more recreational vehicles are sold with gas engines than diesel engines. This might make it harder to find diesel fuel in a city or town.
- If you want to know when to change a fuel filter, refer to your owner's manual.
- Some manufacture the fuel filters built into the fuel tank assembly.
- Figure out if your vehicle has an inline filter that can be serviceable. Most diesel will have that because of how the diesel fuel works within the system.

Section 2 of 4:

Benefits of Diesel Engines

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Diesel engines are usually better for driving long distances. These vehicles might have larger upfront costs than gas-powered cars, but their fuel efficiency often makes them greater investments. If you do a lot of highway driving, or you just rack up a lot of driving time in your day-to-day life, a diesel vehicle might be the one for you. Usually, drivers make up for the initial cost of a diesel vehicle after driving about 30,000 miles (48,300 km).^{[8]
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Diesel engines have a lot of torque, making them great for towing. When it comes to vehicles, torque refers to the strength of the engine. When a car has more torque, it usually accelerates quicker and pulls heavy objects with less effort, even when going up steep inclines. So, if you’ve got a boat or RV to tow, a diesel vehicle can make it easier on you.^{[9]
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A diesel engine uses less parts, which often means it needs fewer repairs. Generally, fewer parts can malfunction in a diesel engine because it doesn’t use spark plugs or distributors to work. The thickness of diesel fuel also has a protective factor, keeping the engine running smoothly for a longer period of time than gas engines.^{[10]
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Section 3 of 4:

Benefits of Gas Engines

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Gas engines are usually better for city driving. If you’re mostly just zipping from the suburbs to the city, a gas-powered engine is probably the better choice for you. The lower cost of these vehicles, and their fuel, makes them great for start-and-stop traffic and driving a shorter total distance per year, compared to diesel cars.^{[11]
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Gas engines typically have more horsepower and can go faster. While torque helps your car get going, horsepower helps it keep going. Gas engines tend to weigh less than diesel engines, which means they can complete more revolutions per minute (RPM) and go faster.^{[12]
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- This is the reason why sports cars are typically gas-powered, while transport trucks use diesel. Sports cars need the greater horsepower of a lightweight engine and fuel to fly down a race track, while trucks need lots of torque to pull their cargo.
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Gas engines might need more repairs, but they’re often less expensive. With the addition of spark plugs and distributors in gas engines, more parts can malfunction and get damaged in a gas engine. However, gas-powered vehicles tend to be more common than diesel vehicles. So, their parts are typically more widely available and cost less to fix.^{[13]
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Section 4 of 4:

Which type of engine is better?

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For long distances and towing, choose diesel. When it comes to choosing a diesel or gas vehicle, think about what you want and need from a car. If you do a lot of driving each year and need to transport heavy items like boats and RVs, a diesel vehicle is likely the more fuel-efficient and cost-effective option.^{[14]
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For high-performance and short distances, go with gas. If you mainly drive through the city and want a car that can do it fast, a gas vehicle is what you’re looking for. They’re usually less expensive than diesel cars too!^{[15]
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