Production on the Suburban and Tahoe began in December 2013 with the first completed SUVs being used for testing purposes. GM then officially started shipping the vehicles to dealerships on February 5, 2014. It is estimated that it takes 8–10 weeks to assemble the SUVs, save for the upgrades on the level trims and destination scheduling. Features The front fascias of the Chevy Suburban and GMC Yukon XL are distinct, but from the base of the A-pillars back, they share most of the same styling cues. This now includes inlaid doors that tuck into the door sills, instead of over them, improving aerodynamics, fuel economy, and lessens interior noise. The hoods and liftgate panels are made of aluminum to reduce vehicle weight, and the wiper blades that were located on the liftgate door were moved to the rear spoiler located on the top of the rear liftgate window. Also noticeable is the SUV's length, which expands from (the Yukon XL's length is shorter at ) and its width from , while the height decreases from , thus allowing the vehicle to become slightly leaner, a little bit wider, more streamlined, and roomier. A more efficient, direct-injected EcoTec3 V8 powertrain (5.3 for the Suburban, 6.2 for Yukon XL/Yukon Denali XL) coupled with improved aerodynamics, helped the SUVs offer greater estimated highway fuel economy and improving its fuel economy estimates to (city), (highway), and (combined) for 2WD, and (city), (highway), and (combined) for 4WD. The increased fuel economy also vaulted the Suburban/Yukon XL into the top spot among large SUVs with the most efficient fuel economy rating numbers for this segment. However, when Motor Trend (which placed the 2015 Suburban on the front cover of its June 2014 issue) did a road test review on the SUVs, it estimated the 4WD MPG on the Suburban LTZ to be slightly better at around city and highway, while the 4WD Yukon Denali XL, whose fuel economy (MPG) is rated at city and highway, was estimated lower at city and highway. Like the 2007–14 version, both the Suburban and Yukon XL do not share a single piece of sheet metal or lighting element with the brands' full-size pick-up trucks (GMC Sierra and Chevy Silverado), and the front grilles of both vehicles are slightly altered to give it their own identity. The front headlights feature projector-beam headlamps that flank the Chevrolet-signature dual-port grille – chrome on