If you are in the market for a new pickup truck, you may be wondering if you should get a gas engine or a diesel engine since there are significant differences between the two. Those differences vary for mid-size, light-duty full-size and heavy-duty full-size pickups.
Which is best for you? Let’s look at the differences between the two engine types, focusing not only on the engines themselves but also on the components that are different between them.
As with all things automotive, there is no perfect answer here. Diesel is known to last hundreds of thousands of miles. Some people even joke that they aren’t even fully broken in until you hit 100,000 miles. Pre-2005 diesel trucks had very few emissions requirements and therefore didn’t have the same emissions systems that new diesel engines have. Generally speaking, diesel engines are built with stronger engine blocks and internals to handle the significantly higher compression ratios when compared to gas engines. Because of this, they tend to handle being worked harder for longer periods of time than gas engines.
If the engine only occasionally has a heavy load placed on it, gas engines can last just as long. Last year, Toyota traded trucks with a man who had put 1 million miles on his Tundra with the 4.7-liter V-8 gas engine. With newer diesels, the engines may be just as durable as the diesels of old. However, due to stricter emissions restrictions, there are a variety of other pricey components that will affect the longevity of the truck. Also, if you want a manual transmission in a full-size truck, your only option is the Ram with the Cummins diesel on the 2500 and 3500 trucks. For those planning to keep their trucks for a long time, manual transmissions are generally less expensive to operate.
Generally, the maintenance on a diesel will cost more than on a gas engine. Diesels hold more oil, making it more expensive to change. Between the fuel and exhaust systems, there are a lot of filters and components that will need changing that you won’t find on a gas engine. New diesel engines also require diesel exhaust fluid, which needs to be added to meet emissions requirements.
Diesels run at lower rpm, which reduces wear on many engine components. Where the diesel can make up for the higher cost of operation is when it is run hard for long periods of time. Under those conditions, gas engines are likely to have more costly internal failures than diesel engines.
Fifteen years ago, it was common to see 25-plus mpg from a heavy-duty diesel engine. Now, most real-world drivers see less than 20 mpg. On the other hand, light-duty and mid-size diesel trucks today can see EPA ratings up to 30 mpg. If the truck is used to haul lighter loads for long distances, then a half-ton or mid-size diesel might be the best choice — again, diesel engines perform best when heavily loaded. A heavily loaded diesel will generally return higher mpg than an equally loaded gas engine.
In short, if a heavy-duty pickup is needed day in and day out, a diesel engine will likely save money on fuel. If the truck will only be hauling a small load or be driven empty, a mid-size pickup with a diesel will cost less in fuel to drive than a comparable truck with a gas engine.
One other thing to consider is the availability of fuel for gas or diesel: For populated areas, this isn’t an issue, but in some areas, it may be harder to find diesel fuel than gasoline.
Cost of Ownership
Advantage: Use- and Class-Dependent
Once again, this depends on how the pickup truck is being used. If it’s hauling heavy loads daily and is going to be used for more than 200,000 miles before being replaced, a diesel is likely going to be less expensive in the long run. If the main use for the truck is to pull a camping trailer that’s well below the maximum towing capacity of the truck — or to look cool while getting groceries — then a gas engine will likely be less expensive overall. Upfront costs for a heavy-duty diesel can be more than $10,000 greater than an equivalent gas engine. This cost goes toward the engine itself, the stronger transmission and drivetrain, and additional emissions components.
For mid-size and light-duty pickup trucks, a diesel engine offers significant fuel mileage improvements, and the diesel option is only around $3,000-$5,000 more than the gas.
If the truck is accumulating a lot of miles each year, better fuel mileage can make up for the additional cost of the diesel engine within a few years. Typically, that includes paying a little more money for diesel fuel over gasoline.
The final thing to consider, which often gets overlooked, is the resale price of the truck. Pickups with diesel engines historically retain a higher value than comparable gas-powered trucks.
For towing, a diesel engine is almost always the better option. Diesels have a lot of torque at low rpm, which is what you want when towing. They get better fuel mileage when heavily loaded and last longer. Another nice aspect about most diesel engines is the integrated exhaust brake. This greatly helps in controlling the truck and trailer when descending steep hills or when driving in traffic. The exhaust brake slows the truck by using back pressure from the turbo to slow the engine down. Having this additional method of braking reduces the wear and tear on the brake system, and it reduces the likelihood of the brakes overheating.
Trucks with gas engines are often rated with a higher payload capacity than the equivalent truck with a diesel because diesel engines and their associated systems weigh significantly more than their gas counterparts. The power of a diesel and the exhaust brake will still be helpful when hauling a heavy payload, but if the truck is being pushed to its limits, then the lighter weight of the gas engine will allow for a higher payload.
The obvious choice for power in the heavy-duty market is the diesel. Gas engines today just don’t compare to diesels when it comes to torque. Ford, GM, and Ram all push more than 900 pounds-feet of torque in their one-ton pickups; gas equivalents don’t even top 500 pounds-feet. A diesel is suited for a hard day’s work and will be able to perform where a gas engine simply can’t.
For light-duty and medium-duty pickups, the torque advantage achieved from the diesel doesn’t overcome the horsepower of the equivalent gas engines. For example, the 2017 Chevrolet Colorado with the baby Duramax only has 181 horsepower but a respectable 369 pounds-feet of torque; the 3.6-liter V-6 gas engine has 308 hp and 275 pounds-feet of torque. The extra horsepower from the faster-revving and higher-revving gas engines make them quicker for spirited driving. The diesels in these classes are designed for maximum efficiency while still being able to get most jobs done. In the heavy-duty class, the engines are designed for maximum power while still being reliable.
Many people may be upset at the opinion that gas is the better engine for off-roading, but there are compelling reasons for it. The heavier weight of the diesel at the front of the truck can be detrimental to off-road driving if the vehicle gets stuck in mud or sand. Gas engines also rev faster and redline higher. This gives them a wider operating rpm range in each gear, good for desert running and clearing mud from the tires.
Automatic transmissions are so good these days, the higher rpm range of a gas engine isn’t as much of a benefit over a diesel as it once was. Diesels — especially when equipped with manuals — offer more low-speed control for rock crawling. The slow-revving low-end torque is great for getting the vehicle to move up steep inclines without spinning the tires. Also, with the extra torque from a diesel, the truck will have an easier time turning oversized tires. The kings of factory off-road trucks include the Ford F-150 Raptor with the 3.5-liter EcoBoost:
And the Ram 2500 Power Wagon with the 6.4-liter Hemi:
Both are available with gas engines only. The new off-roader being built by Chevy, the Colorado ZR2, can be equipped with either a gas or diesel engine. For overlanding rather than strict off-roading, diesels are the engine of preference for improved fuel economy and longevity. In other parts of the world, diesel engines are used extensively as they are often more reliable and can handle lower-quality fuel. Organizations like the Red Cross, the Peace Corps and the U.N. use diesel-equipped Jeeps, Land Rovers and Land Cruisers because of their reliability in rough, dusty, dirty conditions.
There is no obvious winner between a gas and diesel engine. Each one performs better in certain areas; it all comes down to how the truck is going to be used and what the owner prefers.