What is the gas mileage on a 6.6 L v8?
There isn’t a single fuel economy figure for a 6.6 L V8; mpg varies by the exact vehicle, drivetrain, payload and how you drive. In general, full-size trucks equipped with a 6.6 L V8 gasoline engine deliver mpg in the teens, with highway numbers often higher than city driving.
What the “6.6 L V8” means in today’s trucks
The label 6.6 L V8 describes engine displacement, not a fixed mileage rating. Several automakers offer 6.6-liter V8 engines for heavy-duty pickups, but only some are gasoline-fed. For example, General Motors uses a 6.6-liter V8 gasoline engine in its heavy-duty Silverado/Sierra line (often referred to as the L8T family) alongside a separate Duramax 6.6 L diesel. Different model years, configurations, and transmissions affect fuel economy, so the exact mpg figure must be checked for the specific truck you’re considering.
Typical fuel economy ranges for common configurations
The following ranges reflect rough EPA-style estimates for common 6.6 L V8 gasoline setups in full-size pickups and HD trucks. Actual numbers depend on year, drivetrain, gearing, towing/payload, and other options.
- City driving: roughly 12–15 mpg
- Highway driving: roughly 17–22 mpg
- Combined: roughly 15–19 mpg
Note that these ranges are broad benchmarks. Real-world mileage can be higher or lower based on load, towing, tire type, and maintenance. Always consult the OEM window sticker or fueleconomy.gov for your exact configuration.
Factors that influence mpg in practice
Several variables can swing a 6.6 L V8’s mpg up or down. Understanding them helps set expectations beyond a generic number.
- Drivetrain: two-wheel drive vs. four-wheel drive can change efficiency, especially in city conditions.
- Towing and payload: heavier loads reduce fuel economy significantly, especially in start-stop traffic or uphill pulls.
- Transmission and gearing: taller or shorter gears influence engine RPM and efficiency at highway speeds.
- Vehicle weight and aerodynamics: added equipment, bed campers, and aerodynamic resistance matter more than you’d think in a large V8 truck.
- Maintenance and tires: proper maintenance, correct tire pressure, and worn components can improve or degrade mileage.
- Driving style and terrain: aggressive acceleration, frequent braking, and hilly terrain lower mpg; steady speeds and gentle acceleration help.
To maximize accuracy, check official EPA ratings for your exact model and configuration, and consider real-world testing in your typical driving conditions.
How to find the precise mpg for your vehicle
Use these steps to determine the exact fuel economy for a specific truck with a 6.6 L V8 gasoline engine.
- Look up the model and year on fueleconomy.gov to see the official EPA estimates for your drivetrain and trim.
- Review the OEM window sticker or official brochure for your vehicle’s exact configuration (drivetrain, axle ratio, tires, and transmission).
- Check onboard trip computer readings over a representative mix of city and highway driving.
- Perform a controlled mpg test: drive a planned route at a steady speed with your typical payload, then compute mpg from fuel added divided by miles driven.
Finding the precise number for your specific setup will give you the most reliable expectation for daily use and help you compare against other powertrain options.
Bottom line
There is no single mpg figure for a 6.6 L V8 engine. Expect mpg in the mid-teens to low twenties depending on configuration, payload, and driving conditions. For accurate numbers, always consult the EPA estimates for your exact model and configuration and consider real-world testing to reflect your typical usage.
Summary
A 6.6 L V8 gasoline engine does not come with a universal mileage rating. Typical combined fuel economy sits roughly in the 15–19 mpg range, with city mileage around 12–15 mpg and highway mileage around 17–22 mpg, varying by drivetrain, towing, payload, and year. Always verify with EPA ratings for your specific truck and configuration, and factor in payload and driving conditions when estimating real-world mpg.
