Small decreases to city and combined mpg.
Without automatic engine stop-start, the standard-length 2021 GMC Yukon loses 1 mpg city and 1 mpg combined when equipped with the naturally aspirated 5.3L V8 L84, including both rear-wheel drive and four-wheel drive configurations. The feature’s absence also leads to a 1-mpg decrease in the city and combined when equipped with the naturally aspirated 6.2L V8 L87 and rear-wheel drive, while models with the L87 and four-wheel drive lose 1 mpg combined.
The 2021 GMC Yukon is also offered with the 3.0L I6 LM2 turbodiesel Duramax, which continues to come equipped with automatic engine stop-start. All three engines mate to a 10-speed automatic transmission.