It’s Official: 2027 Silverado EPA Ratings Dip, and Our Trail Boss Takes the Biggest Hit
When the first 2027 Silverado window stickers surfaced last week, we broke down what those early numbers meant for our truck and promised to circle back once the EPA made it official. Now, that day is here. The 2027 Silverado EPA ratings are now live on fueleconomy.gov, covering the new 5.7-liter V8, the new 6.6-liter V8, and the 3.0-liter Duramax diesel.
The good news? Every number we reported from those early window stickers held up. The not-so-good news? In fact, compared to 2026, nearly every gas and diesel Silverado takes a small step back. On top of that, our own truck, Cheyenne, takes the biggest hit of all.
2027 Silverado EPA Ratings vs. 2026 at a Glance
Here’s how each 2027 configuration compares to the closest 2026 equivalent. Specifically, for the gas engines, that means the new 5.7-liter V8 against the outgoing 5.3-liter V8, and the new 6.6-liter V8 against the 6.2-liter V8 it replaces.
| Engine and Setup | 2026 MPG (City/Hwy/Combined) | 2027 MPG (City/Hwy/Combined) | Change in Combined MPG (%) |
|---|---|---|---|
| 5.3L V8 vs. 5.7L V8, 2WD | 16/20/17 | 15/19/17 | No change |
| 5.3L V8 vs. 5.7L V8, 4WD | 15/19/17 | 15/18/16 | Down 5.9% |
| 5.3L V8 vs. 5.7L V8, 4WD with mud-terrain tires | 15/18/16 | 14/16/14 | Down 12.5% |
| 6.2L V8 vs. 6.6L V8, 4WD | 15/20/17 | 14/18/15 | Down 11.8% |
| 6.2L V8 vs. 6.6L V8, ZR2 | 14/17/15 | 13/15/14 | Down 6.7% |
| 3.0L Duramax diesel, 2WD | 23/28/25 | 22/27/24 | Down 4.0% |
| 3.0L Duramax diesel, 4WD | 22/25/23 | 21/23/22 | Down 4.3% |
| 3.0L Duramax diesel, 4WD with mud-terrain tires | 21/24/23 | 21/22/21 | Down 8.7% |
| 3.0L Duramax diesel, ZR2 | 20/23/21 | 20/22/21 | No change |
In short, only two setups hold steady: the 2WD 5.7 and the diesel ZR2. Everything else drops one or two MPG combined.
Still No 2027 EPA Ratings for the 2.7-Liter TurboMax
So far, the 2.7-liter TurboMax hasn’t posted official numbers for 2027. For reference, the 2026 version earned 20 MPG combined in 2WD and 19 in 4WD, so we’ll update you once its ratings arrive.
How the 5.7-Liter V8 Stacks Up Against the 5.3
As we expected from the window stickers, the new 5.7-liter V8 matches the outgoing 5.3 at 17 MPG combined in 2WD. In 4WD, however, it slips from 17 to 16 combined, and the highway rating drops from 19 to 18 MPG.
In exchange, the 5.7 makes 402 horsepower and 428 lb-ft of torque, up 47 horsepower and 45 lb-ft over the 5.3. Better yet, it still runs on regular 87 octane. According to the EPA’s annual fuel cost estimates, a 4WD 5.7 costs about $3,900 a year to fuel, compared to $3,650 for a 4WD 5.3.
How Silverado V8 MPG Has Changed Since 1999
To put the new numbers in perspective, we looked at the mainstream V8 from the first model year of each Silverado generation. Since the EPA has updated older ratings to its current testing method, the numbers compare fairly across the years. To illustrate, here’s how combined MPG changed from one generation to the next.
| First Year of Generation | V8 Engine | 2WD Combined MPG | Change From Previous Generation | 4WD Combined MPG | Change From Previous Generation |
|---|---|---|---|---|---|
| 1999 | 5.3L V8, 4-speed | 16 | Silverado debut | 15 | Silverado debut |
| 2007 | 5.3L V8, 4-speed | 17 | Up 6.3% | 16 | Up 6.7% |
| 2014 | 5.3L V8, 6-speed | 19 | Up 11.8% | 18 | Up 12.5% |
| 2019 | 5.3L V8, 8-speed | 19 | No change | 18 | No change |
| 2027 | 5.7L V8, 10-speed | 17 | Down 10.5% | 16 | Down 11.1% |
The biggest jump came in 2014, when the EcoTec3 5.3-liter V8 and a six-speed automatic pushed combined MPG up more than 11%. After that, the 2019 redesign held that line, but the 2027 truck gives most of it back, dropping about 11% in both 2WD and 4WD. As a result, a 4WD 2027 Silverado V8 now matches the 2007 truck on combined fuel economy.
Even so, today’s V8 still comes out 6% to 7% ahead of the original 1999 Silverado, while making far more power. For Trail Boss fans, though, the comparison is tougher. The 2019 Trail Boss with the 5.3 and eight-speed was rated at 17 MPG combined, so Cheyenne’s 14 MPG rating is roughly 18% lower.
Why Cheyenne Takes the Biggest Hit
Our green Custom Trail Boss rides on mud-terrain tires, which puts it in its own category in the 2027 Silverado EPA ratings. As a result, with the 5.7, that setup is rated at 14 MPG city, 16 MPG highway, and 14 MPG combined. That’s also two MPG below the 2026 5.3 with mud-terrains and two MPG below the 16 combined we estimated in our first story.
On top of that, the Custom Trail Boss can’t be ordered with the new 34-gallon fuel tank, so Cheyenne is stuck with the 24-gallon tank. Altogether, at 14 MPG combined, that works out to about 336 miles between fill-ups, roughly 48 fewer than the 384 miles we originally estimated. On a long highway stretch at 16 MPG, though, we could still see about 384 miles.
According to the EPA, the mud-terrain 5.7 costs about $4,450 a year to fuel. In other words, those aggressive tires add roughly $550 a year compared to a standard 4WD 5.7. Consequently, for our family road trips, that likely means planning for one more fuel stop on longer drives.
The 6.6-Liter V8 Gives Up Two MPG
The bigger 6.6-liter V8 replaces the 6.2-liter V8, and it still recommends premium fuel. For instance, on a 4WD Silverado, it’s rated at 14 MPG city, 18 MPG highway, and 15 MPG combined, down from 15/20/17 for the 6.2. Similarly, the ZR2 slips one MPG combined, from 15 to 14.
In return, the 6.6 makes 481 horsepower and 501 lb-ft of torque, compared to 420 horsepower and 460 lb-ft from the 6.2. Even so, the EPA puts its annual fuel cost at about $5,150 on a 4WD truck, roughly $600 more than the 6.2. Fortunately, the 34-gallon tank comes standard with the 6.6 on the High Country, which should stretch it to around 510 miles of combined driving.
Even the Duramax Diesel Slips
Surprisingly, the 3.0-liter Duramax diesel loses ground too. For example, in 2WD, it drops from 25 to 24 MPG combined, and in 4WD, it falls from 23 to 22. Meanwhile, mud-terrain models see the biggest drop, from 23 to 21 combined, while the ZR2 holds steady at 21.
Since most of those losses show up in the highway ratings, changes to the redesigned truck itself may play a role. Still, the diesel remains the efficiency leader of the gas and diesel lineup, with a 2WD model rated at 27 MPG on the highway.
Our Take on the 2027 Silverado EPA Ratings
Historically, bigger engines and more power usually come with a small fuel economy penalty, and that’s exactly what happened here. Fortunately, for most buyers, one or two MPG won’t be a deal breaker, especially with the extra horsepower and torque.
For us, though, the mud-terrain number stings a bit. Still, we’d make the same choice again. The 5.7 runs on regular gas, it tows up to 13,700 pounds, and Cheyenne’s look is exactly what we wanted. Once our truck arrives and finishes its break-in period, we’ll track every fill-up and share how close it gets to its 2027 Silverado EPA ratings.
More From Our Silverado Coverage
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