The 2020 GMC Sierra 1500 follows up on a complete overhaul for the nameplate arriving for the preceding 2019 model year. Buyers have a total of six different engines to choose from, each of which gets its own fuel economy ratings. Now, we’re taking a closer look at the GMC Sierra fuel economy numbers in the following GM Authority Comparison.
Looking over our compiled 2020 GMC Sierra fuel economy numbers, we find the most fuel-efficient engine option to be the Duramax turbo-diesel 3.0L LM2 I6 , which posts a max of 23 mpg in the city, 30 mpg on the highway and 26 mpg combined when connected to 2WD. Add in 4WD, and those figures drop to 22 mpg in the city, 26 mpg on the highway, and 24 mpg combined. In both instances, the LM2 connects to the GM 10-speed automatic transmission.
On the gasoline side of things, the most fuel-efficient engine option is the turbocharged 2.7L L3B I4, which mates to the GM eight-speed automatic transmission. Fuel returns for the L3B are rated at 20 mpg in the city, 23 mpg on the highway, and 21 mpg combined when connected to 2WD, and 19 mpg in the city, 22 mpg on the highway, and 20 mpg combined when connected to 4WD.
The least fuel-efficient engine is the naturally aspirated 5.3L L82 V8, which provides 15 mpg in the city, 21 mpg on the highway, and 17 mpg combined when connected to 2WD, and 14 mpg in the city, 18 mpg on the highway, and 16 mpg combined when connected to 4WD.
Interestingly, the GMC Sierra fuel economy numbers aren’t that different between the various gas engines. For example, the range-topping naturally aspirated 6.2L L87 V8 is rated at 15 mpg in the city, 20 mpg on the highway, and 17 mpg combined when connected to 4WD. Those ratings just so happen to match the ratings for the base-level naturally aspirated 4.3L LV3 V6 when connected to 4WD. However, the L87 produces substantially more power and torque than the LV3, with 420 horsepower and 460 pound-feet compared to the V6’s 285 horsepower and 305 pound-feet. The L87 also requires premium fuel, though.
It’s also worth pointing out that the turbocharged 2.7L L3B I4 gets the exact same highway fuel economy rating as the naturally aspirated 5.3L L84 V8, although the latter is also offered with the optional Fuel Economy Package (XFE), which boosts the highway rating by one additional mpg.
To note, the Fuel Economy Package (XFE) adds 18-inch six-spoke machined aluminum wheels (UHN) with Dark Grey Metallic accents, all-season blackwall tires (QDF), and a Premium soft roll-up tonneau cover (VPB).
So, with that covered, here are the GMC Sierra fuel economy fuel economy figures:
| RPO Code | Engine | Aspiration | Fuel | Power (hp / kW @ RPM) | Torque (lb-ft / Nm @ RPM) | Transmission | Drive Wheels | City MPG | Highway MPG | Combined MPG |
|---|---|---|---|---|---|---|---|---|---|---|
| LV3 | 4.3L V6 | Atmospheric | Gasoline | 285 / 212 @ 5300 | 305 / 413 @ 3900 | 6-speed auto | 2WD | 16 | 21 | 17 |
| L3B | 2.7L I4 Turbo | Turbo | Gasoline | 310 / 231 @ 5600 | 348 / 471 @ 1500 | 8-speed auto | 2WD | 20 | 23 | 21 |
| L3B | 2.7L I4 Turbo (base Sierra) | Turbo | Gasoline | 310 / 231 @ 5600 | 348 / 471 @ 1500 | 8-speed auto | 2WD | 19 | 22 | 20 |
| L82 | 5.3L V8 AFM | Atmospheric | Gasoline | 355 / 265 @ 5600 | 383 / 518 @ 4100 | 6-speed auto | 2WD | 15 | 21 | 17 |
| L82 | 5.3L V8 AFM E85 capable | Atmospheric | Gasoline | 355 / 265 @ 5600 | 383 / 518 @ 4100 | 6-speed auto | 2WD | 15 | 19 | 16 |
| L84 | 5.3L V8 DFM | Atmospheric | Gasoline | 355 / 265 @ 5600 | 383 / 518 @ 4100 | 8-speed auto | 2WD | 17 | 23 | 19 |
| L84 | 5.3L V8 DFM (XFE Fuel Economy Package) | Atmospheric | Gasoline | 355 / 265 @ 5600 | 383 / 518 @ 4100 | 8-speed auto | 2WD | 17 | 24 | 20 |
| LM2 | 3.0L I6 Turbo Diesel | Turbo | Diesel | 277 / 206.6 @ 3750 | 460 / 623.7 @ 1500 | 10-speed auto | 2WD | 23 | 30 | 26 |
| LV3 | 4.3L V6 | Atmospheric | Gasoline | 285 / 212 @ 5300 | 305 / 413 @ 3900 | 6-speed auto | 4WD | 15 | 20 | 17 |
| L3B | 2.7L I4 Turbo | Turbo | Gasoline | 310 / 231 @ 5600 | 348 / 471 @ 1500 | 8-speed auto | 4WD | 19 | 22 | 20 |
| L82 | 5.3L V8 AFM | Atmospheric | Gasoline | 355 / 265 @ 5600 | 383 / 518 @ 4100 | 6-speed auto | 4WD | 15 | 20 | 17 |
| L82 | 5.3L V8 AFM E85 capable | Atmospheric | Gasoline | 355 / 265 @ 5600 | 383 / 518 @ 4100 | 6-speed auto | 4WD | 14 | 19 | 16 |
| L82 | 5.3L V8 AFM (AT4) | Atmospheric | Gasoline | 355 / 265 @ 5600 | 383 / 518 @ 4100 | 6-speed auto | 4WD | 14 | 18 | 16 |
| L84 | 5.3L V8 DFM | Atmospheric | Gasoline | 355 / 265 @ 5600 | 383 / 518 @ 4100 | 8-speed auto | 4WD | 16 | 22 | 18 |
| L84 | 5.3L V8 DFM (AT4) | Atmospheric | Gasoline | 355 / 265 @ 5600 | 383 / 518 @ 4100 | 8-speed auto | 4WD | 16 | 21 | 18 |
| L84 | 5.3L V8 DFM | Atmospheric | Gasoline | 355 / 265 @ 5600 | 383 / 518 @ 4100 | 10-speed auto | 4WD | 16 | 22 | 19 |
| L87 | 6.2L V8 DFM | Atmospheric | Gasoline* | 420 / 313 @ 5600 | 460 / 624 @ 4100 | 10-speed auto | 4WD | 15 | 20 | 17 |
| L87 | 6.2L V8 DFM (AT4) | Atmospheric | Gasoline* | 420 / 313 @ 5600 | 460 / 624 @ 4100 | 10-speed auto | 4WD | 15 | 19 | 17 |
| LM2 | 3.0L I6 Turbo Diesel | Turbo | Diesel | 277 / 206.6 @ 3750 | 460 / 623.7 @ 1500 | 10-speed auto | 4WD | 22 | 26 | 24 |
- * Premium fuel recommended.
These GMC Sierra fuel economy numbers line up with differing engine availability, as determined by the various trim levels on offer. Check out a complete breakdown of engine availability in the table below.
| RPO Code | Engine | Aspiration | Fuel | Sierra (base) | SLE | Elevation | SLT | AT4 | Denali |
|---|---|---|---|---|---|---|---|---|---|
| LV3 | 4.3L V6 | Atmospheric | Gasoline | S | |||||
| L3B | 2.7L I4 Turbo | Turbo | Gasoline | A | S | S | |||
| L82 | 5.3L V8 AFM | Atmospheric | Gasoline | A | |||||
| L84 | 5.3L V8 DFM | Atmospheric | Gasoline | A | A | S | S | S | |
| L84 | 5.3L V8 DFM (XFE Fuel Economy Package) | Atmospheric | Gasoline | A | |||||
| L87 | 6.2L V8 DFM | Atmospheric | Gasoline* | A | A | A | |||
| LM2 | 3.0L I6 Turbo Diesel | Turbo | Diesel | A | A | A | A | A |
- * Premium fuel recommended.
Which engine do you prefer? Let us know in the comments, and make sure to subscribe to GM Authority for more GMC Sierra news, GMC news, and around-the-clock GM news coverage.
Comments
That is really crappy gas mileage for the 5.3 4WD!
That’s because it’s the lifted and Duratrac AT/MT tire outfitted base Sierra AT4 with the old 5.3 and old-old-old 6 speed trans. Option the AT4 SLE with new 5.3 and 10spd and mileage jumps 3mpg combined (+4mpg on highway). To do so the package is about +$4500 but you get a lot of other features included in the package.
Which makes zero zero zero sense considering the same old 5.3 AFM and 6 speed in the 2020 Yukon/Tahoe get BETTER highway mileage and the same combined figure than the all new models which use the new DFM 5.3 and 10 speed automatic and actually lose up to 3 highway and 2 combined in many combinations. The mileage ratings on most of these all new lighter trucks make no sense whatsoever. How does the 4.3 get the same mileage as the 6.2 in the new truck yet in the old truck it got 2-3 better despite being heavier? Why is the identical GMC version of the GM pickups rated for up to 3 MPG worse mileage using the same new diesel engine and 10 speed automatic compared to the Silverado?
There is indeed something totally bizarre with the way these new trucks are being rated and Gm is shooting themselves in the foot by underrating certain combinations so much because i know for a fact that most any of these setups will easily exceed the combined and highway figures by up to 3 MPG!
They’re lighter, yes, but the Sierra/Silverado are also larger, punching a bigger hole in the air. This decreases fuel efficiency. Compare the old engine/transmission combinations and it becomes evident how much more efficient the new offerings really are. Makes you wonder what would happen if you put the new pairing into the old trucks, what would those numbers be?
The 2020 AT4 with the 5.3 has a 10sp transmission, not an 8.
I own a 2020 sierra 1500 crewcab 4×4 evolution
My high mileage is average 29 mpg my best is 32.6!
City is a bit less then advertised mpg its 20-23 but I live on the top of a decent hill…like ikae gantlet steep.. other wise it would be 25 mpg for sure… it’s amazing for a pick up
I’m assuming you have the diesel engine. If so you are exceeding the highway rating by 3-5 MPG and further proving my point regarding how they rate these things.
Yes I guess I would have commented on that…
I would choose the 3L turbo diesel