Diesel Engines vs Gas Engines

If you’re trying to decide between a diesel and a gas engine for your truck, the short answer is: diesel wins for heavy hauling and long miles, gas wins for lighter loads and lower upfront cost. But the right choice depends on your specific operation. This guide breaks down the real differences in purchase price, fuel economy, maintenance, and resale so you can make a smart call.

Upfront Cost: What You Pay at the Dealer

Diesel engines typically add $6,000 to $10,000 to the sticker price of a new truck compared to a gas engine. For example, a 2026 Ford F-250 with a 6.7L Power Stroke diesel costs about $10,000 more than the same truck with a 7.3L gas V8. In the medium-duty segment, a diesel-equipped Freightliner M2 or International MV can run $8,000 to $15,000 more than a gas version.

If you’re buying used, expect to pay a premium for diesel too. A 5-year-old diesel pickup might cost $5,000 to $8,000 more than an equivalent gas model, depending on mileage and condition.

Fuel Economy and Cost Per Mile

Diesel engines are 20% to 35% more fuel-efficient than gas engines, especially under load. A typical diesel pickup gets 18 to 22 mpg empty and 12 to 15 mpg towing 10,000 pounds. A gas truck gets 14 to 17 mpg empty and 8 to 10 mpg towing the same load.

But diesel fuel often costs more per gallon. As of early 2026, the national average for diesel is around $3.80 to $4.20 per gallon, while regular gasoline averages $3.00 to $3.40. So the fuel cost per mile is closer than you might think.

Here’s a real-world example for a truck driving 20,000 miles a year, half of it towing:

• Diesel: 15 mpg average, 1,333 gallons, at $4.00/gal = $5,332 per year
• Gas: 11 mpg average, 1,818 gallons, at $3.20/gal = $5,818 per year

That’s a savings of about $486 per year with diesel, but it would take over 12 years to recoup the $6,000 upfront cost difference. If you drive 60,000 miles a year, the payback drops to about 4 years.

Maintenance and Repairs: What to Expect

Diesel engines generally last longer, but they cost more to maintain. Here’s the breakdown:

• Oil changes: Diesel takes 10 to 15 quarts of oil; gas takes 5 to 8 quarts. A diesel oil change runs $100 to $200, gas is $50 to $100. Intervals are similar: 5,000 to 7,500 miles.
• Fuel filters: Diesel has two filters, replaced every 15,000 to 25,000 miles, costing $50 to $150 in parts. Gas has one filter, often good for 30,000+ miles, costing $20 to $50.
• Emissions systems: Diesels have DEF (diesel exhaust fluid) and DPF (diesel particulate filter). DEF adds $10 to $20 per 2.5-gallon jug, and you’ll use about 2 to 3 gallons per 1,000 miles. DPF cleaning or replacement can cost $2,000 to $5,000 if it fails.
• Longevity: A well-maintained diesel can go 500,000 to 1,000,000 miles. A gas engine typically lasts 200,000 to 300,000 miles.

Towing and Payload Capacity

Diesel engines produce more torque at lower RPMs, which makes them better for pulling heavy loads. For example, a 2026 Ford F-350 with the 6.7L diesel makes 1,050 lb-ft of torque, while the 7.3L gas V8 makes 468 lb-ft. That translates to a max tow rating of 22,000 pounds for the diesel vs 15,000 pounds for gas.

In medium-duty trucks, the gap is even wider. A diesel Class 6 truck can handle 25,000 to 35,000 pounds GCWR, while a gas version tops out around 20,000 to 25,000 pounds.

Resale Value and Depreciation

Diesel trucks hold their value better. After 5 years, a diesel pickup might retain 60% to 65% of its original value, while a gas truck retains 50% to 55%. That’s partly because buyers want diesel for towing and longevity. However, if you put high miles on a truck, the resale advantage narrows.

Comparison Table: Diesel vs Gas for Pickups and Medium-Duty Trucks

Factor	Diesel	Gas
Upfront cost	$6,000-$10,000 more	Baseline
Fuel economy	20-35% better	Lower
Fuel cost per gallon	$3.80-$4.20	$3.00-$3.40
Annual fuel cost (20k mi, half towing)	~$5,300	~$5,800
Oil change cost	$100-$200	$50-$100
Typical engine life	500k-1M miles	200k-300k miles
Max tow (pickup)	20,000-22,000 lbs	12,000-15,000 lbs
Resale after 5 years	60-65% of original	50-55% of original

Practical Steps to Decide This Week

1. Calculate your annual mileage and typical load. If you drive over 40,000 miles a year or tow more than 10,000 pounds regularly, diesel may pay off. If you’re under that, gas is likely cheaper.
2. Get quotes for both engines on the exact truck you want. Include financing costs, because a higher loan amount means more interest.
3. Check your local fuel prices. Use a site like AAA or GasBuddy to see the current spread between diesel and gas in your area.
4. Ask about warranty. Diesel engines often have a 5-year/100,000-mile warranty, but emissions components may have separate coverage. Gas engines typically have a 3-year/36,000-mile bumper-to-bumper.
5. Talk to a mechanic who works on both. Ask about common issues for the specific engine you’re considering, like injector problems or turbo failures.

FAQ

Is a diesel engine worth it for a local delivery truck?

Probably not. Local routes mean lots of idling and short trips, which can clog the DPF and increase maintenance costs. A gas engine is cheaper to buy and maintain, and you won’t see the fuel savings because you’re not driving enough miles.

Can I use a gas truck for heavy towing occasionally?

Yes, but you’ll feel the difference. Gas engines need higher RPMs to make power, so you’ll downshift more on hills and get worse fuel economy while towing. If you tow over 10,000 pounds more than a few times a month, diesel is the better tool.

What about the new diesel emissions systems? Are they reliable?

Modern diesels are reliable if you drive them hard enough to regenerate the DPF. If you do a lot of highway miles, the system works as designed. If you mostly idle or drive short distances, you’ll have problems. Gas engines have fewer emissions components, so they’re simpler.

How much does it cost to replace a diesel engine vs a gas engine?

A new diesel engine can cost $10,000 to $20,000 installed, while a gas engine runs $5,000 to $10,000. But diesel engines rarely need replacement before 500,000 miles if maintained.

The Bottom Line

Choose diesel if you regularly tow heavy loads, drive high annual mileage, or plan to keep the truck for many years. Choose gas if you want the lowest upfront cost, do mostly local or light-duty work, and don’t need maximum towing. Run the numbers for your specific situation, and you’ll know which engine puts more money in your pocket.