Detroit still plays the displacement game, and General Motors is king of the hill for the time being with its 8.3-liter Duramax for heavy-duty workhorses. Beginning with the 2027 model year, the GMC Sierra HD bids farewell to the 6.6-liter iteration of the Duramax in favor of the largest diesel in the segment. Codenamed Mongoose, this engine costs a fair bit of money.

         

Pricing information released by General Motors puts it $11,400 above the 6.6-liter naturally aspirated small-block V8 gasoline engine, or $1,410 higher than GMC's listing for the 2026 truck with the 6.6-liter diesel. That's only part of the price increase buyers will see on the window sticker and online configurator, though.