# 2027 GMC Sierra V8 Power vs Efficiency

> The 2027 GMC Sierra's V8 engine delivers more power but less fuel efficiency than the Duramax diesel.
- Title: 2027 GMC Sierra V8 Power vs Efficiency · Motor1 | Shortify
- Summary: The 2027 GMC Sierra's V8 engine delivers more power but less fuel efficiency than the Duramax diesel.
- Keywords: gmc, sierra, duramax, fuel economy, 2027, truck, Motor1
- Source: Motor1 — https://motor1.com/news/814635/2027-gmc-sierra-v8-mpg
- Author: Brian Potter
- Published: 2026-11-06T09:44:09+00:00
- Read time: 1 min
- Topics: gmc, sierra, v8, duramax, fuel economy, 2027, truck, cars
## 2027 GMC Sierra V8 Engine Ratings
The 2027 GMC Sierra's V8 engines post lower combined fuel economy than the Duramax diesel across all trim levels.
## 2027 V8 Fuel Economy Figures
Two-wheel-drive 5.7-liter V8: 15 mpg city, 19 mpg highway, 17 mpg combined. Four-wheel-drive 5.7-liter V8: 16 mpg city, 20 mpg highway, 18 mpg combined.
## 2027 Duramax Diesel Ratings
Two-wheel-drive Duramax: 23 mpg city, 28 mpg highway, 25 mpg combined. Four-wheel-drive Duramax: 22 mpg city, 26 mpg highway, 24 mpg combined.
## V8 vs Outgoing Engines
The new 5.7-liter V8 replaces the 5.3-liter with more power but lower mileage. The 6.6-liter V8 replaces the 6.2-liter with more power but lower mileage.
## Key takeaway

The 2027 GMC Sierra's V8 engines produce more power but lower combined fuel economy than the Duramax diesel across all trim levels.