This truck-based SUV is a twin of the Chevrolet Suburban. The third-row seat in the XL is a bit roomier than the one in the shorter GMC Yukon, and there is plenty of cargo room when that row is raised. Power comes from a 5.3-liter V8 and a six-speed automatic that returns 16 mpg and feels slightly sluggish. It's too bad that you have to opt for the expensive Denali version to get the Magnetic Ride Control suspension, which improves ride comfort and handling response. The 6.2-liter engine on the Denali is also a meaningful upgrade, but it significantly increases the price. Properly equipped, the XL can tow 8,500 pounds, its only advantage over a car-based SUV. Lane-keeping assist and Apple CarPlay capability are available. Reliability has been well below average.