Diesel engines have been around since the late 1800s, and in the decades since they’ve grown from a novelty in the world of power generation into the driving force of industries the world over. We’re taking a look at some of the pluses and minuses of these revolutionary machines to help you decide if a diesel engine is right for you. 

Some of diesel engines’ biggest drawbacks have been substantially improved in recent years, such as their penchant for polluting, loud noise, and difficulty starting in cold weather. However, there are still a couple of issues to consider before jumping on-board the diesel train, just so you know what to expect. 

 

Pro: Powerful

Diesel engines are the workhorses of the power industry. They’re installed in the heavy-duty trucks, container ships, and trains, used for towing the biggest loads and meeting the most demanding prime power generation needs. 

Although diesels aren’t known for horsepower, their chief ability is in the torque they can provide, which is much more than a similarly sized gasoline engine can muster. Torque is what gives them the “oomph” needed to get up to speed and get work done at low power, making them great at towing and accelerating quickly out of the gate. 

 

Pro: Efficient

Diesel engines are inherently more efficient than gasoline engines because of their combustion method and lower fuel consumption. Unlike gas or petrol engines, which use a spark plug to ignite the air-fuel mixture in the combustion chamber, the diesel engine compresses the air inside until it’s hot enough to spontaneously ignite the fuel when it is sprayed into the chamber. (Speaking of which, no spark plugs or distributors also means no ignition tune-ups for diesels.)   

When it comes to fuel, diesel contains up to 15% more energy than gasoline, allowing diesel cars to travel up to 35% farther on a gallon of fuel, according to the U.S. Department of Energy. 

To learn more about why diesel engines are so efficient, check out our article on the subject. 

 

Pro: Reliable

This is one of the primary reasons so many backup generator owners opt for diesel-powered units: diesel engines are about as dependable as it gets. Because they have to be able to withstand the higher compression during operation, diesel engines are typically built to be more rugged, which can lend them longer lifetimes than other engines.

However, it’s important to note that diesel engines are no different than gas or other types of engines when it comes to the need for routine maintenance. A well-cared-for modern gasoline engine may last as long as a diesel engine. It’s also true that tighter environmental regulations for diesel engines have altered the long-standing fact that diesel engines are simpler machines with fewer moving parts–the new technology that’s required to achieve these standards can wear out, no matter what type of engine it’s in. 

To read more about the lifespan of a particular type of diesel engine, see our article on how long diesel generators last. 

 

Pro: Good Resale Value

Diesel engines’ performance have earned them a great reputation, one that is reflected when it comes time to remarket one. Consumers in the market for pre-owned engines are looking for ones that have a lot of life left in them and won’t be a big fixer-upper project to get them in working order. A diesel that’s seen regular maintenance checks all these boxes and commands a premium price.

 

Con: Prone to Wet Stacking

Hindered performance and even permanent damage are the negative consequences of a diesel engine that falls victim to wet stacking. 

This problem, applicable only to engines that run on diesel, results from operating the engine for long periods of time below the necessary operating temperature, with an incorrect air-to-fuel ratio, or too much or too little fuel. Any one of these scenarios can cause unburned fuel to gather in the exhaust system in the form of black ooze. 

Nevertheless, responsible owners who follow best practices as laid out in their manual will never experience this potential disadvantage of diesel engines. 

 

Con: Fuel is More Expensive

Diesel fuel was historically lower-priced than gasoline, but that has changed since around the turn of the millenium. Several factors have contributed to this, including popular demand for diesel, higher production costs due to stricter environmental standards, and a higher federal excise tax on diesel than on gasoline. 

In addition, in 2014 the Environmental Protection Agency established standards that require minimum refill levels of an additive called diesel exhaust fuel (DEF) for both road and non-road diesel engines. DEF helps reduce the amount of nitrous oxide from entering the atmosphere by converting it to separate molecules of nitrogen and oxygen. Although it’s better for the environment and improves performance, DEF is still an added cost for diesel owners to contend with. 

Still, because diesel engines are so efficient, their fuel costs per kW of power produced is still typically lower than that of other engines, making this “con” often a moot point.