GM boasts among the most powerful and efficient engines in the truck segment, thanks to AFM, though our experiences have been disappointing. Only the Denali’s 6.2-liter engine gets the six-speed auto; all others are mated to a four-speed. There’s a 4.3-liter V6 rated at 195 horsepower at 4,600 rpm and 260 lb.-ft of torque at 2,800 rpm; a 4.8-liter V8 making 295 horsepower at 5,600 rpm and 305 lb.-ft. of torque at 4,800 rpm; and a 5.3-liter FlexFuel V8 with AFM that gets 315 horsepower at 5,200 rpm and 338 lb.-ft. of torque at 4,400 rpm. For even more power – and maximum towing – there’s a 6.0-liter V8 with AFM that makes 367 horsepower at 5,500 rpm and 375 lb.-ft. of torque at 4,300 rpm.