The 2027 Chevrolet Silverado 1500 and GMC Sierra 1500 Get Worse Fuel Economy Numbers

The 2027 Chevrolet Silverado 1500 and GMC Sierra 1500 are getting major updates, including new small-block V-8 engines, updated transmissions, and refreshed exterior and interior designs. Those changes bring revised EPA fuel economy ratings, and the numbers point to a small efficiency hit for most configurations compared with the 2026 trucks.

The EPA has released ratings for the 5.7-liter V-8, 6.6-liter V-8, and 3.0-liter turbodiesel available in both trucks; final fuel economy figures for the base 2.7-liter turbo-four are still pending. According to data from GM Authority, nearly every listed powertrain and trim combination returns lower ratings for 2027. The exception is the GMC Sierra AT4X equipped with the turbodiesel.

The V-8 changes help explain some of the decline. The 5.3-liter V-8 has been replaced by a 5.7-liter engine, while the 6.2-liter V-8 gives way to a 6.6-liter V-8. Both engines have larger displacements and more horsepower and torque, which in some cases can also mean more fuel consumption. The diesel is a more surprising case: It keeps the same 3.0-liter displacement, yet some 2027 configurations are rated as much as 3 mpg lower than their 2026 counterparts.

The tables below compare city, highway, and combined EPA ratings for the 2027 Silverado and Sierra with the previous 2026 models. The amount of the change varies by engine, drivetrain, and trim. In several configurations, the difference is only 1 or 2 mpg, while certain four-wheel-drive diesel versions have larger drops. Choosing a different drivetrain or trim can therefore affect the comparison as much as the engine itself.

The Sierra AT4X with the 3.0-liter turbodiesel stands out as the only configuration with improved ratings. It gains 1 mpg in city driving and 2 mpg on both the highway and combined cycle. For the remaining configurations, the 2027 ratings are generally worse across city, highway, and combined driving. The final figures for the 2.7-liter turbo-four will complete the comparison once the EPA publishes them.