Basics of diesel cars

Though diesel, like gasoline, is usually distilled from petroleum, it's fundamentally different than gasoline in a couple of important ways. First, it's a combustible oil and not a solvent. Second, compression ignites diesel rather than a spark. These characteristics — an oil and compression ignition — are responsible for most of the differences in how gas and diesel cars perform.

Pros and cons of diesel cars and trucks

Despite historically representing a tiny fraction of the US car market, diesel cars and trucks have been popular in the rest of the world for decades and are a growing segment of the US car market. If you're wondering if diesel trucks or cars are worth it, consider the pros and cons of diesel cars and trucks.

Pros of diesel cars and trucks

Longevity. Diesel engines are extraordinarily reliable and tend to last a very long time. In fact, several cars holding records for high mileage have diesel engines, like the famous Mercedes-Benz 240D that logged almost 3 million miles before being retired. Diesel engine longevity is primarily due to two factors. The engines are built more durably to handle the compression force of the ignition cycle, and the fuel itself is an oil that gently lubricates the engine as it runs.

Gasoline, by comparison, is a solvent that dissolves oil and tends to cause increased wear in the engine.

Efficiency. Though diesel cars and trucks may cost more upfront, they're often worth it in the long run. Diesel is a richer source of usable energy than gasoline. According to the Department of Energy, diesel motors typically get as much as 35% more miles to the gallon.

More torque. The high compression ratio of diesel vehicles generates more torque, making diesel engines a better choice for pulling or hauling lots of weight.

More torque. The high compression ratio of diesel vehicles generates more torque, making diesel engines a better choice for pulling or hauling lots of weight.

Lower CO2 emissions. There's some debate about the environmental impact of diesel compared to gasoline-powered cars, but modern diesel vehicles produce less CO2 per gallon of fuel than comparable gasoline-powered engines.

Slower depreciation. According to a study by the University of Michigan Transportation Research Institute, diesel cars and trucks depreciate much more slowly than their gasoline counterparts.

Cons of diesel cars and trucks

There's a lot to like about diesel engines, but they have drawbacks for some drivers:

Best for highway miles. To get the most benefit from a diesel engine, you need to log many miles on the highway, where engine design and increased fuel economy shine. In fact, if you do most of your driving in short-distance, low-speed city driving, you may end up clogging the engine's particulate filter, requiring additional maintenance.

They aren't always as fun to drive. Diesel has been the fuel of choice in trucking for decades because it favors torque over top speed. While modern diesel engines have improved power and can now offer high-performance speeds, sporty driving still generally favors gasoline-powered engines.

Upfront cost. Diesel engines tend to cost several thousand dollars more when you buy a new car, and you need to own the vehicle for at least a few years to break even on that difference in savings.

Maintenance cost. Diesel engines generally need less frequent maintenance than gasoline-powered vehicles. But when service time comes, diesel usually costs more to repair or maintain. Be prepared for higher recurring costs, even if they come less often.

Should I buy a diesel car or truck?

That depends on what kind of driver you are and how you drive most of the time. Diesel is a great choice for working vehicles that log many long trips on the highway or frequently need to pull big loads. Because of that, diesel trucks are often worth it, and diesel cars can be worth it for those who frequently travel long distances. Drivers who keep the same vehicle for a long time may benefit from diesel more than those who prefer to change cars after five years or less.

If you're mostly driving in the city, making short trips at relatively low speeds, you're less likely to reap significant benefits from a diesel engine. However, you may still appreciate their reliability and fuel economy. If you're looking for a sporty ride or love performance driving, there are some options available, but you may find gasoline-powered cars a better fit.