Diesel or Gas: Which is a Better Investment for Your Fleet?

When you have a fleet to carry out your business operations, that fleet needs to get from point A to point B. The question is, how do you do it?
These days, your options include traditional gasoline and diesel, as well as electric vehicles and hybrids, and even vehicles powered by natural gas or hydrogen. The investment in alternative fuel, though, tends to be significant, and the vehicles themselves are very costly, so for most fleet managers, the decision comes back to petroleum products. Which is the better option, gas or diesel? Let’s talk about it.
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Evaluating Diesel and Gas
The most important thing to recognize right off the bat is that there’s no right answer here. Diesel and gas are both good fuels and, in many ways, are very comparable, especially compared to newer technologies and alternative propulsion. Each one is better in different circumstances, so it’s important to evaluate your fleet’s needs and make decisions on a per-vehicle basis.
Truthfully, once your fleet reaches a certain size, you’re generally going to end up with different types of vehicles using different types of fuel. Mixed fleets are common, after all.
Let’s talk about different specific elements to consider and whether diesel or gas is the better option for each.
The Initial Cost of the Vehicle
First and foremost, one of the biggest factors in the minds of many fleet managers is the initial cost to purchase or lease the vehicle. When you’re building or expanding a fleet or replacing an older and worn-out vehicle, you need to pay close attention to the cost of the vehicle you obtain. We’ve talked before about whether or not it’s better to lease or buy and whether it makes more sense to buy new or used, but the biggest determining factor is often the up-front costs and whether or not your business can afford the purchase.
When looking at two comparable vehicles, you will generally find that the diesel vehicle is more expensive. They’re heavier, bulkier, expected to last longer, and usually have a greater capacity than a comparable gasoline engine, so the truck is considered more powerful and higher quality. Frequently, that comes with a higher price tag.
On the scale of commercial vehicles, though, the difference in price might not be that significant. If you’re looking at a vehicle that costs $80-90k, a price difference of $5k isn’t necessarily hugely significant, especially spread out across the length of a lease or loan.
As far as used vehicles go, diesel vehicles tend to maintain their condition better for longer, so a vehicle several years old is likely going to be more expensive if it’s a diesel vehicle because it’s expected to be in better condition. This may vary based on the make, model, and previous usage of the vehicle.
This also applies to the resale value of the vehicle over time. Gasoline-powered vehicles tend to depreciate in value faster, so when it comes time to sell an existing vehicle and replace it, you won’t get as much out of a gasoline engine.
Longevity and Duration of the Engine
As we’ve already mentioned, diesel engines are generally expected to maintain their condition and durability for longer than comparable gasoline vehicles. Diesel engines are simpler in design and can be made in stronger ways, with fewer small parts and pieces subject to wear and damage. The more complex elements of a diesel, like the exhaust filtering system, are separate and can be repaired or replaced without having to tear down the engine itself.
Another benefit to diesel in this position is that, since diesel is a more energy-dense fuel and can deliver more torque, it doesn’t need to run as fast, which means it produces less heat and less wear, has less chance of gumming up the engine, and lasts longer.
Diesels are, broadly speaking, the clear winner when it comes to the long-term durability and longevity of the engine.
Wear, Tear, and Repair
Over time and with use, any engine will need inspections, preventative maintenance, and repair for damaged or broken components.
On the surface, diesel engines come out ahead here, too. They have fewer parts that need to be repaired or replaced, like spark plugs, and have fewer seals and gaskets that can wear out over time. They have similar profiles for things like oil changes, and all of the modern computer systems are roughly as prone to failure across the board while also depending heavily on the manufacturer and their choice of parts.
The downside is that when a repair is necessitated, it’s going to be more difficult and more costly on a diesel. Since diesels are generally simpler, their parts are larger and require more teardown to replace, and while that certainly can be done, the parts may be harder to find or in shorter supply, the work is more intensive (leading to greater labor costs) and finding OEM parts can be difficult for some models.
It’s important to remember, as well, that while diesel may be more resilient to damage from wear and tear compared to gasoline, diesel vehicles are often used in much more stressful environments, so the wear and tear put on them per mile can be higher, so depending on the usage you have for the vehicle, it can balance out.
Fuel Economy for Different Types of Trips
One of the most commonly cited benefits of the diesel engine over the gasoline engine is better fuel efficiency. The trouble is, this might not actually be true, and it depends entirely on the kind of usage you have for your vehicles.
Vehicles that go on long trips over the highway are going to benefit from diesel. This is one of the two ideal situations for diesel engines, where the higher energy capacity of diesel fuel and the lower operating stress of the diesel engine provide a better long-term ride.
The other situation where a diesel generally benefits is for high-weight or high-power requirements. Diesels deliver more torque to the wheels, so hauling extremely heavy loads or operating heavy equipment will benefit from diesels.
Many drivers like the greater fuel economy of long-haul diesel over gasoline because it means they don’t have to stop to fuel up as often, but this can be subjective; other drivers like the excuse to stop and stretch their legs.
On the other hand, gasoline is better for start-and-stop operations, for shorter trips, and where idling is a necessity. Diesels and gasoline engines burn fuel as they idle, but diesel costs more for that fuel, so it balances out. Meanwhile, gasoline is more insulated from the inefficiencies of the engine when starting and stopping are constant.
There’s no easy way to determine which will be better for you short of harvesting appropriate telemetry of your actual usage and comparing it over time. A good benchmark is that when a vehicle exceeds around 35k miles per year, diesel may start to be more efficient.
Engine Power and Capacity
This is something we’ve touched on already. Diesel engines have more power per ounce of fuel and are thus able to haul heavier loads and perform maneuvers that require more torque and power than gasoline engines. This isn’t an issue in mid-weight usage, but for heavy-duty and up, it’s essential.
This is not to say that a diesel vehicle can’t be used for lighter-duty operations, only that it’s not as efficient to do so, so you end up wasting that power and capacity when you don’t actually need it. This is a significant part of right-sizing your fleet; not just choosing the number of vehicles you need, but the capacity you need to get out of them.
Fuel Availability and Cost
While both gasoline and diesel are broadly available across the country, there are certain areas where finding diesel fuel can be more difficult, and not all diesel pumps are positioned or designed for larger vehicles. You may need to find specialized commercial fuel stations, which might mean driving out of your way to do so. Meanwhile, typical gasoline is available virtually everywhere.
Some fleets will set up their own fuel stations and maintain their own fuel stocks. This alleviates the need to worry about just about any of this, outside of trips long enough that your drivers can’t stop back at home base to refuel.
Cost for fuel, meanwhile, is a different story. Gasoline costs are lower than diesel costs by a significant margin, and while gasoline engines need to fuel up more often, the expenses can often be roughly the same when the balance sheet is calculated.
Emissions and Environmental Impact
The image of a truck accelerating and blasting black smoke into the air is iconic of a diesel, but it’s actually not very accurate these days; federal regulations and local laws mandate the use of exhaust filtration systems on diesels that filter and purify exhaust to reduce emissions. It’s not as though the fuel burns cleaner, of course, just that the byproducts are caught in the DEF system.
Gasoline engines have their own similar system, the catalytic converter, also meant to reduce emissions. A catalytic converter generally never needs much in the way of maintenance, whereas a diesel exhaust filter will need to be regularly cleaned and the DEF fluid replaced. That’s another added cost to the arrangement as well.
Diesels also have strict emissions control standards, while gasoline engines aren’t necessarily as tightly regulated. On the other hand, catalytic converters are a frequent target of theft, while a truck’s diesel exhaust filters aren’t.
Susceptibility to Environmental Factors
Another consideration is the weather. In particular, very hot and very cold conditions can be relevant. Diesel engines are generally more resilient to hotter temperatures because they don’t generate as much of their own heat or run as hot as gasoline. Extremely hot conditions can affect both kinds of engines, though.
Very cold weather, meanwhile, is worse for diesel. This is because diesel fuel can thicken and “gel” when it’s cold out. In fact, diesel can gel up at temperatures as “high” as 10-15 degrees Fahrenheit; given that winters in the northern part of the country can fall below zero for days or weeks at a time, this can be a significant issue. There are additives and options to help prevent or reverse this, but it’s a consideration that gasoline doesn’t have.
Alternative Fuels
It can also be worth examining options for other fuels.
Diesel vehicles may be able to use biodiesel, which can be a more environmentally friendly fuel. This isn’t really true at the engine level, though; biodiesel can be dirtier and not properly filtered with a standard diesel exhaust system. Instead, it’s more environmentally friendly to manufacture than petroleum products.
Gasoline, meanwhile, can often be found with a hybrid system using an electric motor as well. This has pros and cons; the battery systems add a lot of weight, and while a hybrid system adds a ton of fuel efficiency, recharging can be very time-consuming.
Hydrogen and natural gas vehicles have their own pros and cons as well, but these are different enough that it’s outside the scope of this discussion. If you want us to examine these options, feel free to let us know!
Picking the Right Truck for Your Fleet
Picking the right vehicle with the right kind of fuel for your fleet is an important decision you need to make every time you want to acquire a new vehicle. The truth is, you’ll very likely end up with both. Lighter-duty pickups, passenger vehicles, and even short-distance box trucks and similar vehicles may be more beneficial with gasoline engines. Meanwhile, operations that require more power or longer-distance travel can benefit more from diesel systems.
Either way, when your fleet needs maintenance, we’re here to help. Whether it’s commercial diesel motors, standard gasoline engines, or a mixture of both, our nationwide network of fleet service providers knows exactly how to help. All you need to do is find a service provider near you and reach out to get started with a fleet relationship and maintenance contract. With that, we can help you keep your entire fleet rolling, from the first mile of a brand-new gasoline truck to the millionth mile of your most resilient diesel.