The Cost of Comfort: GM's Full-size SUVs Gain Thrift in City Driving, Lose It on the Open Road

Steph Willems
by Steph Willems
the cost of comfort gms full size suvs gain thrift in city driving lose it on the

The revamped, full-size Chevrolet Tahoe and Suburban and their GMC Yukon/Yukon XL twins gain significant length, interior volume, and creature comforts for 2021, but extra MPGs seem to be in short supply.

The vehicles are now even larger than their predecessors, are still heavy, and carry identical V8 engine displacements, so no one should have expected Prius fighters. Still, the changes in fuel economy are worthy of note.

Still unlisted on the EPA’s fuel economy site, the models had their MPG figures released by GM this week. What we can see is that, while efficiency sees a gain in the city, that improvement is offset by decreased thriftiness on the highway.

It breaks down like this: in 5.3-liter, RWD or 4WD, short-wheelbase guise, the 2021 GM full-sizers rate 16 mpg city, 20 mpg highway, and 18 mpg combined. The previous-generation 5.3L short-wheelbase models earned 15/22/18 in rear-drive guise, 15/21/17 with four-wheel motivation.

The lengthier 5.3L models match these figures in rear-drive form, but lose 1 MPG in each driving cycle when equipped with four-wheel drive. EPA ratings for the old-gen 5.3L long-wheelbase models stand at 15/22/18 (RWD) and 14/21/17 (4WD).

Inclusion of a standard 10-speed automatic and GM’s Dynamic Fuel Management helped the V8 manage its thirst around town, but it seems all the new added hardware (tech niceties, independent rear suspension, size) causes the hulking SUVs to imbibe more heavily on the highway. Highways are for AAA, not AA, it seems.

Opt for the 6.2-liter in either the Tahoe or Suburban, and the EPA rating comes out to 16/20/18 regardless of driveline type. No penalty here for going bigger (minus the cost, of course). The new models in 6.2L guise slightly top their predecessors in both city and combined economy.

It all sounds unimpressive, until you consider GM’s decision to offer the company’s new 3.0-liter Duramax inline-six diesel in all such models (including the Cadillac Escalade). Boasting 277 horsepower and 460 lb-ft of torque, the Duramax variants’ MPG rating remains unknown, but one look at the Chevy Silverado’s ratings suggests significant improvements in efficiency for so-equipped models. Chris was pleased with what he saw in a recent test of a new Duramax-powered Silverado 1500.

[Images: General Motors]

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  • RSF RSF on May 07, 2020

    No one cares about a MPG rating on these. What matters to me, much more than ever, is how much of this thing consists of Chinese parts.

  • Jerome10 Jerome10 on May 07, 2020

    Do I have it right that these went from AFM (4 or 8 cylinder only) to DFM (any cylinder combo from 1-8 at any time) and went from 6 speed to 10 speed transmissions.... And got basically zero MPG improvement? If so why bother? And if this isn’t an indication we’re scraping the bottom of the barrel when it comes to ICE and transmission efficiency gains I’m not sure what is.

  • Jim Bonham Thanks.
  • Luke42 I just bought a 3-row Tesla Model Y.If Toyota made a similar vehicle, I would have bought that instead. I'm former Prius owner, and would have bought a Prius-like EV if it were available.Toyota hasn't tried to compete with the Model Y. GM made the Bolt EUV, and Ford made the Mach-E. Tesla beat them all fair and square, but Toyota didn't even try.[Shrug]
  • RHD Toyota is trying to hedge their bets, and have something for everyone. They also may be farther behind in developing electric vehicles than they care to admit. Japanese corporations sometimes come up with cutting-edge products, such as the Sony Walkman. Large corporations (and not just Japanese corporations) tend to be like GM, though - too many voices just don't get heard, to the long-term detriment of the entity.
  • Randy in rocklin The Japanese can be so smart and yet so dumb. I'm America-Japanese and they really can be dumb sometimes like their masking paranoia.
  • Bunkie The Flying Flea has a fascinating story and served, inadvertently, to broaden the understanding of aircraft design. The crash described in the article is only part of the tale.
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