Why Oil Companies May Love the 2027 Chevrolet Silverado’s Lower Mileage

V8 ratings move downward

Documents posted by GM Authority show lower ratings for Silverados equipped with either the new 5.7-liter or 6.6-liter V8. Across city, highway and combined measures, the declines are generally between 1 and 2 mpg.

The 5.7-liter V8 earns ratings of 16 mpg city, 19 highway and 17 combined with two-wheel drive. Four-wheel drive lowers the highway and combined figures by another mpg; compared with 2026, the city and combined ratings fall by 1 mpg and the highway rating by 2.

The larger V8 and ZR2

The 6.6-liter V8 is listed only with four-wheel drive, at 14 mpg city, 18 highway and 15 combined. Those figures are each lower than the previous model year by either 1 or 2 mpg.

For the off-road Silverado ZR2, city and combined ratings drop by 1 mpg, while highway mileage falls by 3 mpg. The article says the same change should apply to the GMC Sierra AT4X equivalent.

Diesel changes and missing data

Most 2027 Silverados with the 3.0-liter inline-six turbodiesel return 1 to 2 mpg less than last year. Some four-wheel-drive trims keep the same city rating, and the diesel ZR2’s city and highway figures remain unchanged. Fuel-economy ratings for the turbocharged 2.7-liter four-cylinder have not been published.

Sales magnify small declines

The Silverado usually ranks second among U.S. best-selling vehicles, behind the Ford F-Series, while the Sierra also sells in large numbers. Through the third quarter of 2026, GMC sold 252,639 Sierras and Chevrolet sold 413,383 Silverados.

Production of the redesigned trucks began in October. The article notes that not every truck will have a V8, but says the scale of sales means even a 1-mpg decline in V8 mileage could substantially increase total fuel use.