My wife proudly informed me that it is a 6 Liter turbo diesel.
Go wife! That would be the
GM Duramax.
From the wiki entry:
L5P The L5P duramax is the latest version of the Duramax V8 diesel engine.(engine code Y) Introduced in the 2017 model year it is the most powerful diesel engine GM has produced with 445 hp (332 kW) at 2,800 rpm and 910 lb⋅ft (1,234 N⋅m) at 1,600 rpm. Design spec performance can exceed 550 bhp (410 kW) at 3050 rpm and 1,050 lb⋅ft (1,424 N⋅m) at 1975 rpm.
I'm guessing a few more tweaks for the Beast...