Diesel vs. Gas Trucks: Which Should You Buy?

Engine Overview: Qualities, Features, and Traits

What are the differences between gas and diesel engines, anyway? 

For starters, gasoline and diesel fuel are drastically different in their characteristics and chemical composition, even though both are derived from crude oil. Gasoline is a lighter, more volatile fuel with a lower boiling point. It's made of shorter hydrocarbon chains and is highly flammable. Alternatively, diesel is a heavier, less volatile fuel with a higher boiling point. Unlike gasoline, diesel is made of longer hydrocarbon chains and is far less flammable.

In addition to the type of fuel each requires for combustion, the overall design and methods of combustion differ between gasoline and diesel powerplants.

Gasoline

Every fossil-fuel-burning engine requires three ingredients to run—fuel, air, and ignition. While diesel and gasoline engines inhale the same air, they receive fuel and ignition from different sources. Gasoline engines ingest—you guessed it—gasoline as their fuel source. During combustion, a mixture of gas and air enters the combustion chamber, where a spark ignites it. 

Diesel

On the other hand, diesel engines ingest diesel fuel, which requires a different ignition source. Rather than utilizing a spark, diesel engines employ compression ignition. As air is compressed in the cylinder, it superheats to temperatures well above 400 degrees Celsius. Diesel fuel is then injected into the cylinder, which ignites instantaneously, leading to a similar combustion as in a gasoline engine.

Efficiency: Energy Usage and Fuel Economy

Now that we understand the differences in the design and operation of both engines, how do these factors apply to real-world situations? Regarding efficiency, gas and diesel engines offer drastically different fuel economy figures.

Gasoline

Gasoline is more volatile than diesel, meaning it burns faster and more violently. While this may seem beneficial to an internal combustion engine, the opposite is true, as maximizing gasoline's efficiency has proven difficult.

Measures must be taken to slow gasoline's burning. In the mid-20th century, engineers employed lead-infused gasoline to slow the combustion process, allowing for a more comprehensive burn and more energy to be extracted from the fuel. Modern-day fuels employ other less harmful additives to boost octane levels, achieving the same result. However, these measures still don't match the efficiency of a diesel engine.

Diesel

Alternatively, diesel engines, with their higher compression ratios and compression ignition process, enable fuel to be burned more efficiently. These factors, paired with diesel engines' relatively low operating temperatures compared to their gasoline counterparts and the more energy-dense fuel source, enable diesel engines to produce more energy per unit volume of fuel.  

In less technical terms, diesel produces more energy than gasoline from the same fuel volume, resulting in greater overall efficiency. Unfortunately, the diesel combustion process also produces higher levels of particulate matter and nitrogen oxides, though modern emissions systems are helping to offset these pollutants.

Longevity: Lifespan and Reliability

Next, let's discuss reliability. Diesel engines are notoriously long-lasting and durable, but is that still a selling point with today's advancements in gasoline engines?

Gasoline

Once upon a time, gasoline-powered engines were said to be at the end of their lives around 100,000 miles due to material quality, limited technology, and poor maintenance standards. However, with modern advancements and routine services, it's not outlandish for them to last 300,000 miles without requiring significant repairs. 

Engines like Chevy's LS-based Vortec motors or virtually any of Toyota's I4 or V6 engines from the past few decades can easily touch 200,000 miles on the odometer without significant repairs. But how does that stack up to diesel engines?

Diesel

Diesel engines, regardless of generation, are known for their robust durability and longevity—and for good reason. Motors like the tried-and-tested 5.9L Cummins or 7.3L Powerstroke travel well over 300,000 miles with minimal wear. While most will require costly fuel system refreshes and a transmission replacement or two to reach such milestones, diesel long blocks have proven to be hearty. 

While early iterations of modern emissions systems have tarnished the diesel engine's reputation for reliability—consider the early DPF (diesel particulate filter) systems on 6.7 Cummins engines or the EGRs on 6.4L Powerstrokes—most emissions-centered shortcomings have been addressed by 2025.   

Nowadays, it's not uncommon to find well-loved diesel trucks with 350,000 or more miles that still have life left in them, so long as the body and frame aren't falling apart! However, it's important to account for the more expensive and frequent maintenance costs typically associated with diesel trucks.

Performance: Towing, Hauling, and Power Potential

Lastly, let's talk about performance. The primary reason one may opt for a diesel over a gasoline engine is its heavy-duty performance—namely, its outlandish towing and hauling capacities. 

Those who work in trades positions or frequently tow or haul heavy loads typically prefer the performance of a diesel engine. However, gasoline engines are plenty capable for most of the population.

Gasoline

Gasoline engines are engineered for high horsepower figures compared to torque. These engines typically rev higher than comparable diesel engines and make peak power at higher RPMs. While gasoline engines may not have the gargantuan torque figures of diesel engines, they offer plenty of power for everyday driving and routine hauling and towing—just not to the extremes of diesel engines. However, most gasoline-powered trucks will have no problem towing a 7,000-lb. travel trailer or hauling a bed full of gravel.

Diesel

Alternatively, diesel engines are torque monsters. Rather than focusing on horsepower numbers, they prioritize high torque figures, allowing them to produce power across the entire RPM band, not just at high RPMs. This characteristic lends diesel engines to hard work and rigorous tasks, as they can produce massive amounts of torque from a dead stop or while cruising down the interstate.

In other words, diesel engines are built to work, whether hauling a massive fifth-wheel trailer or a fully loaded car hauler. Diesel engines also respond better to performance modifications than gas engines, such as air intakes, exhaust systems, and programmers.

Which Should You Buy?

So, should you invest your hard-earned dollars into a gas or diesel truck? 

To summarize the points above, gas and diesel trucks both have pros and cons. Starting with the former, gas trucks have a lower initial buy-in and are typically more straightforward and less expensive to maintain. However, they're also less efficient and capable than their diesel-powered counterparts. 

Alternatively, diesel-powered trucks are harder-working and typically last longer, though they're far more expensive to purchase, require more maintenance, and tend to pollute more. So, which is better? 

Gasoline and diesel-powered vehicles both have their place in today's market. Depending on the work they'll be performing, one fuel type may be superior to the other at specific tasks. 

For example, suppose you plan to use your truck exclusively for working and frequently towing heavy loads over long distances. In that case, a diesel truck offers the extra torque and longevity you'll need. However, if your truck is nothing more than a daily driver making occasional trips to the hardware store for DIY projects, consider a gas truck for the lower initial and maintenance costs. 

As always, if you have any additional questions on gas and diesel pickups, like Should You Pick a Diesel Truck in 2025 or What Is a Deleted Diesel, contact our experts and check out the rest of our articles on RealSource.