The available 8.3L Duramax is the heavy-duty diesel in the 2027 Sierra HD. It is a different engine from the 3.0L Duramax in the Sierra 1500. Choose the truck series first, then compare the powertrains available in it.
What the 2027 heavy-duty engines change
GM announced an available 8.3L Duramax Turbo-Diesel V8 rated at 555 horsepower and 1,230 lb.-ft. of torque, plus an enhanced 6.6L gasoline V8 rated at 412 horsepower and 472 lb.-ft. of torque. Both pair with an Allison 10-speed transmission. GM reports up to 38,000 pounds of maximum gooseneck towing on select properly equipped HD configurations; that figure does not apply to every Sierra 2500HD or 3500HD. Verify vehicle-specific trailering and payload limits. GM announcement, September 24, 2026.
When the diesel comparison becomes useful
If you tow a heavy trailer often, bring your typical loaded weight, highway mileage and route. Compare the diesel and gasoline trucks with the same cab, bed and axle configuration; horsepower and torque alone do not tell you what either truck can tow.
Compare ownership for your own mileage
Split your annual miles between loaded and unloaded driving. Use actual fuel quotes and a written maintenance schedule for each powertrain. Compare the extra purchase cost with the operating difference over the time you intend to keep the truck. Frequent towing and occasional local towing can produce very different answers.
Ask for gas and diesel trucks with comparable axle ratios, cabs and beds. Contact Circle Buick GMC in Highland or call 219-227-4410.