Pumping gas in car at gas station

Gasoline vs. Diesel: What's the Difference?

By the Mercury Team

You may have pulled up to the gas pump at your local convenience store, absentmindedly picked up the nozzle at the end of the green hose and spent a few seconds of confusion wondering why it wouldn’t fit into the fuel filler of your car. You eventually realized it was the hose for diesel, not gasoline, and put it back on its holder.

Seeing those hoses at the gas pump might make you wonder: What’s the difference between a gasoline engine and one that runs on diesel fuel, and why would someone choose one over the other?

What’s the Difference Between Diesel and Gas?

Here are some of the similarities and differences between diesel and gas.

Engines 101

Gasoline and diesel engines have a lot in common. Both are internal combustion engines, and each converts the chemical energy in fuel into mechanical energy. Both incorporate pistons that move up and down inside cylinders, with that movement driven by the combustion of fuel in each. Those pistons are attached to a crankshaft, which turns as the pistons move to provide the energy that moves the vehicle.

The difference between the two engines involves the way the fuel is ignited.

Diesel Engines

When most of us think of a diesel engine, what comes to mind are the 18-wheelers we see on the interstate. While it’s true those rigs run on diesel, there are plenty of other diesel-powered vehicles on the road. They aren’t very common in the United States, but in Europe, more than a third of all cars on the road run on diesel fuel.

In a diesel engine, there’s no spark plug. Instead, the compression ignites the air/fuel mixture, creating an explosion that keeps the pistons moving.

Benefits of Diesel

The main advantages of a diesel engine compared with a gasoline one come in terms of fuel efficiency, engine reliability, and power. Because diesel engines are built to withstand higher compression, they tend to be more reliable and last longer than gasoline engines. Diesel fuel is thicker than gasoline, and as such, provides more power and mileage per gallon.

Gas Engines

In a gasoline engine, the fuel is mixed with air in the cylinder. The piston compresses the mixture, which is then ignited by a spark from the spark plug.

Benefits of Gasoline

Gasoline engines are lighter and deliver higher performance than diesel engines. There aren’t diesel engines in sports cars for the same reasons there aren’t gasoline engines in big trucks. In addition, gasoline engines tend to be less expensive to repair simply because they’re more common. 

What Happens If You Use the Wrong Fuel?

If you have ever wondered if you can put diesel fuel in a gas car or vice versa, here’s what you need to know.

What Happens If You Put Gas in a Diesel Engine?

Nothing good happens when you put gas in a diesel engine. As soon as you do this, you throw off the car’s fuel molecular balance and change the fuel’s flashpoint — or when the fuel ignites. This can result in premature ignition and cause substantial damage to your car. 

If you accidentally put gas in a diesel engine, don’t start your vehicle. It will only cause more damage to your engine, meaning a larger repair bill. Call roadside assistance and take your car to your preferred mechanic. 

Can You Put Diesel in a Gas Car?

No. Gas-powered vehicles need gasoline, not diesel. Diesel fuel is thicker than gasoline, so it won’t be able to easily flow into your vehicle. If you accidentally put diesel in your gas car, there likely won’t be a lot of it due to its viscosity. However, even just a small amount of diesel can clog your engine’s fuel injectors, filters, and lines, potentially making your car inoperable. 

Again, don’t start your vehicle if you manage to get diesel in your car. You’ll only exacerbate the problem and increase your repair bill. Have a tow truck take your car to your mechanic to help fix the issue.


If you’re seeking a lightweight passenger car that will go from zero to 60 in the blink of an eye, a gasoline engine is a good choice. If you’re looking for a car to tow a boat to the lake on the weekend, diesel may be the way to go. You also may want to consider getting an electric vehicle (EV). These cars don’t need gasoline or diesel, eliminating tailpipe emissions and giving you a more eco-friendly ride.

Whatever type of car you decide to get, you’ll need auto insurance to protect you on the road. Mercury Insurance provides reliable coverage at an affordable rate.

Contact us for a fast, free quote!

Mercury Team

The Mercury Marketing Team is made up of professionals in the fields of Content Creation, Public Relations and Social Media. The team works together to deliver professionally written and researched content to provide information for consumers.

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