The GMC Yukon is all-new for the 2021 model year, ushering in a fresh fifth generation for the nameplate with a long list of updates and changes. However, as a result of the ongoing microchip shortage, some 2021 GMC Yukon models are no longer equipped with automatic engine stop-start, leading to a decrease to in fuel economy. Now, GM Authority is taking a look at how much of an impact automatic engine stop-start makes to fuel returns for the all-new Yukon.
We previously covered fuel economy figures for a variety of GM models no longer equipped with automatic engine stop-start, including the 2021 GMC Sierra 1500, the 2021 Chevy Silverado 1500, and the 2021 Chevy Suburban, all of which showed minor impacts to fuel economy ratings without automatic engine stop-start. Unsurprisingly, the same is true for the 2021 GMC Yukon.
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.
Below, we’ve also listed the fuel economy figures for the extended-length 2021 GMC Yukon XL, which, like the standard-length model, sees only minor changes without automatic engine stop-start.
| Drivetrain | Engine | Transmission | Auto Stop/Start | City mpg | Highway mpg | Combined mpg | Effective Date |
|---|---|---|---|---|---|---|---|
| 2WD | 5.3L V8 L84 | 10-speed auto | Yes | 16 | 20 | 18 | Start of 2021 MY |
| 2WD | 5.3L V8 L84 | 10-speed auto | No | 15 | 20 | 17 | June 7, 2021 |
| 4WD | 5.3L V8 L84 | 10-speed auto | Yes | 16 | 20 | 18 | Start of 2021 MY |
| 4WD | 5.3L V8 L84 | 10-speed auto | No | 15 | 20 | 17 | June 7, 2021 |
| 2WD | 6.2L V8 L87 | 10-speed auto | Yes | 15 | 20 | 17 | Start of 2021 MY |
| 2WD | 6.2L V8 L87 | 10-speed auto | No | 14 | 20 | 16 | June 7, 2021 |
| 4WD | 6.2L V8 L87 | 10-speed auto | Yes | 14 | 19 | 16 | Start of 2021 MY |
| 4WD | 6.2L V8 L87 | 10-speed auto | No | 13 | 19 | 16 | June 7, 2021 |
| 2WD | Turbodiesel 3.0L I6 LM2 | 10-speed auto | Yes | 21 | 27 | 23 | Start of 2021 MY |
| 4WD | Turbodiesel 3.0L I6 LM2 | 10-speed auto | Yes | 20 | 26 | 22 | Start of 2021 MY |
| Drivetrain | Engine | Transmission | Auto Stop/Start | City mpg | Highway mpg | Combined mpg | Effective Date |
|---|---|---|---|---|---|---|---|
| 2WD | 5.3L V8 L84 | 10-speed auto | Yes | 16 | 20 | 18 | Start of 2021 MY |
| 2WD | 5.3L V8 L84 | 10-speed auto | No | 15 | 20 | 17 | June 7, 2021 |
| 4WD | 5.3L V8 L84 | 10-speed auto | Yes | 15 | 19 | 17 | Start of 2021 MY |
| 4WD | 5.3L V8 L84 | 10-speed auto | No | 15 | 19 | 16 | June 7, 2021 |
| 2WD | 6.2L V8 L87 | 10-speed auto | Yes | 14 | 20 | 16 | Start of 2021 MY |
| 2WD | 6.2L V8 L87 | 10-speed auto | No | 14 | 20 | 16 | June 7, 2021 |
| 4WD | 6.2L V8 L87 | 10-speed auto | Yes | 14 | 19 | 16 | Start of 2021 MY |
| 4WD | 6.2L V8 L87 | 10-speed auto | No | 13 | 19 | 16 | June 7, 2021 |
| 2WD | Turbodiesel 3.0L I6 LM2 | 10-speed auto | Yes | 21 | 27 | 23 | Start of 2021 MY |
| 4WD | Turbodiesel 3.0L I6 LM2 | 10-speed auto | Yes | 20 | 26 | 22 | Start of 2021 MY |
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Comments
No keep this worthless feature off all future vehicles. How about getting rid of the rest of the BS tech while you’re at it. Make better engines and transmissions instead .
Welcome out from under your rock! Things have changed quite a bit since you have been gone.
fuel savings vs cost of a new starter motor that wears out after all the unnecessary extra duty it has to perform? GM says that they are built for heavy duty. So when it comes time to replace it you’re looking at 1000$-to 1500$ plus labour.
Just so they can print questionable Bragg fuel ratings 🤬
Do you have proof of worn out starters?
GM has offered SS for over a half a decade and people are not complaining about starter replacements.
Oh wow, one whole MPG loss. This feature along with AFM/DFM are probably the most overrated features on vehicles nowadays. I drive my Camaro in manual mode pretty much full time and I can still get decent gas mileage with all 8 cylinders running.
Sure the average is 5% savings but these are people hauler and during daily driving stopping could be for a minute or two at a time with multiple stops could be 10-15%.
The stop-start on our Regal TourX could be in engine stop mode for over 2 minutes or more if I cut the climate control. It achieve 30 mpg in mixed driving with AC on mostly do to SS.
AIUI that 1 MPG savings from Autp S/S is an EPA credit, not actual fuel savings. The manufacturers implement it because it helps their CAFE average, thus reducing the credits they have to buy or penalties paid. It wouldn’t surprise me in the least if they get a Covid waiver or credit in lieu of the function. I would gladly pay them to remove it from my 2021 Yukon.