The Yukon XL is, appropriately, longer in both wheelbase and overall length than the 'regular' Yukon, 14 and 20.4 inches, respectively, to be exact. The Extra Length Yukon, then, is more capable at carrying things inside it, and therefore gets a bigger optional engine. New for 2008 is standard stability control and a six-speed automatic for the heavier-duty 3/4-ton models and standard side curtain air bags across the range.

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The 4.8 liter V8 available on the shorty Yukon is nowhere to be found here, replaced by the 5.3 liter V8 as standard equipment. Power is rated at 320 horsepower at 5,200 rpm and 340 lb-ft at 4,200 rpm. This engine is partnered with a four-speed automatic transmission. The combo returns 14 mpg on the EPA's city cycle, and 20 mpg on the highway on two-wheel drive Yukons, or 14 / 20 in four-wheel drives. The Flex Fuel on E85 version fares slightly worse, at 12 / 16 mpg for 2WD models and 11 / 16 mpg on 4WDs.
The optional engine is a 6.0 liter V8 with variable valve timing and Active Fuel Management that makes 366 hp at 5,500 rpm and 380 lb-ft at 4,300 rpm and is available as a standalone option on the SLT trims of the half-ton XL. It also comes with a four-speed automatic.

A 352 hp (at 5,400 rpm and 383 lb-ft at 4,300 rpm) version of that engine is the only motivator on the heavier duty ¾-ton XL. The only transmission on the ¾-tons is a six-speed automatic. The 6.0 liter V8 returns 12 mpg in the city and 17 mpg on the highway.

The half-ton XLs are able to tow a maximum of 7,100 lbs in 2WD guise with the 5.3 liter and 8,100 lbs with the 6.0 liter. Four-wheel drive models with the 5.3 liter can handle 8,000 lbs while the 6.0 liter's maximum towing capacity is 7,900 lbs. The ¾-tons are the real workhorses, however, as they're able to tow 9,700 lbs in 2WD gusie and 9,300 when equipped with 4WD.