Gas or Duramax — which should I get?
Short answer: if you tow heavy and often, go Duramax diesel (975 lb-ft of torque, up to 22,390 lbs of towing). If you plow and tow moderate loads, the standard 6.6L gas V8 saves you money up front and is plenty of truck. We carry the largest crew-cab HD inventory in Maine, so you can compare both side by side in Arundel.
It’s the question we hear most on the heavy-duty lot at Weirs GMC in Arundel. Both 6.6L V8s in the 2026 GMC Sierra 2500HD and 3500HD are seriously capable — they’re just built for different kinds of work. Here’s how to decide between them.
Gas vs. Duramax at a Glance
| 6.6L Gas V8 | 6.6L Duramax Diesel | |
|---|---|---|
| Horsepower | 401 hp | 470 hp |
| Torque | 464 lb-ft | 975 lb-ft |
| Transmission | Allison 10-speed | Allison 10-speed |
| Max conventional towing* | up to ~16,000 lbs | up to ~20,000 lbs |
| Max gooseneck / 5th-wheel* | lower | up to 22,390 lbs |
| Up-front cost | Standard (lower) | About $9,900 more* |
| Best for | Plowing, hauling, moderate towing | Heavy / frequent towing, long hauls |
*Max ratings require proper configuration (cab, bed, drivetrain, rear wheels, and the right trailering package). Ask us for the exact rating on the truck you’re considering.
The 6.6L Gas V8: Capable and Cost-Effective
The standard 6.6L gas V8 makes 401 hp and 464 lb-ft, and for a lot of our customers it’s the smarter buy. It costs less up front, diesel-specific maintenance (DEF, fuel filters) isn’t part of your life, and the lighter engine over the front axle is a real plus for plowing — which matters a lot around here. It’ll still tow up to roughly 16,000 lbs properly equipped, so for a dump trailer, a moderate gooseneck, or a couple of sleds and a loaded bed, it’s more than enough.
Choose gas if: you plow, haul, and tow moderate loads; you don’t tow at max capacity every week; or you want the lowest cost of entry.
The Duramax Diesel: Built to Tow Heavy
The available 6.6L Duramax turbo-diesel is a different animal: 470 hp and a massive 975 lb-ft of torque, backed by the same Allison 10-speed. That torque is what you feel pulling a heavy trailer up a grade without the truck working hard, and the integrated exhaust brake holds you back coming down the other side — a big deal on long descents. It also unlocks the highest tow ratings (up to 20,000 lbs conventional and 22,390 lbs on a properly equipped gooseneck/5th-wheel setup) and generally returns better fuel economy when you’re working it hard.
Choose Duramax if: you tow heavy and often — equipment trailers, big goosenecks, fifth-wheel campers — or you put on serious highway miles under load.
So, Heavy Towing? Diesel Earns Its Premium
The Duramax adds about $9,900 (per the current window sticker), so the honest math is about how you actually use the truck. If you’re regularly near max capacity, the diesel’s torque, towing ceiling, fuel economy under load, and exhaust brake pay you back in capability and comfort — and diesels tend to hold strong resale. If your towing is occasional or moderate and you spend winters plowing, the gas V8 keeps more money in your pocket and does the job. We keep both on the lot in Arundel, so the easiest way to decide is to drive them back to back.
Which Engine Should You Get?
- Plowing + everyday hauling 6.6L Gas V8
- Occasional / moderate towing 6.6L Gas V8
- Lowest up-front cost 6.6L Gas V8
- Heavy towing every week Duramax Diesel
- Gooseneck / fifth-wheel / max capacity Duramax Diesel
- Long highway hauls under load Duramax Diesel
Not Sure Which Engine Fits Your Work?
We carry the largest crew-cab HD inventory in Maine, so you can drive the gas and the Duramax back to back. Tell us what you tow and plow and we’ll match you to the right Sierra HD — minutes from Portland, Kennebunk, and Biddeford.
Shop Sierra HD Inventory Get Pre-Approved Call 207-600-1088Gas vs. Diesel: Frequently Asked Questions
Is the Duramax diesel worth it over the gas V8?
How much can the gas 6.6L V8 tow vs. the Duramax?
Does the diesel get better fuel economy?
Is the gas engine better for plowing?
Do both engines use the Allison transmission?
Can I drive both at Weirs GMC?
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