A 320-horsepower 5.3-liter Vortec engine powers the Yukon XL 1500. With ratings of 15 mpg city and 21 mpg highway, it's a thirsty SUV -- but still beats the Ford Expedition by one mile per gallon. Opt for the 6-liter V8 in the 2500, or the Denali and its 6.2-liter V8, however, and fuel economy ratings dip under the Expedition's.
All Yukon engines offer GM's VVT system, which enables them to run on only four cylinders when full power isn't needed. Also available is an engine-brake feature for towing to avoid excessive brake degradation on downhill grades.
The 1500 and 2500 can both be had with rear-wheel drive or four-wheel drive; the Denali even has an available all-wheel drive system, which is handy if you live in an area prone to foul weather.