Exactly how fast the 2007 GMC Yukon is remains a mystery, but this year’s added engine power can’t hurt. The 4.8-liter V8 is now rated at 290 horsepower, up from 285 last year; and the 5.3-liter V8’s horsepower is up from 295 to 320. That small-block V8 features GM’s Displacement on Demand cylinder deactivation system, and with the redesigned Yukon’s improved drag coefficient, EPA combined fuel economy is expected to rate 20.5 mpg on two-wheel-drive trucks and 20.1 mpg on four-wheel-drive units. That’s up from combined ratings of 16-17 mpg for 2006 models. Yukon Denali models can also be equipped with a new 6.2-liter V8 that features variable valve timing and 380 horsepower complemented by 415 lb.-ft. of torque. This beefy engine will also include Displacement on Demand for the 2008 model year.