15 MPG combined isn’t going to win any awards, but the 2024 GMC Sierra Cab Chassis 4WD 5.3L 8-cyl isn’t built for fuel efficiency awards. It’s built for hard work, for hauling, for plowing, and for serving as the foundation for vocational builds ranging from dump trucks to ambulance conversions. Fuel consumption is lower on the priority list than capability for the people who depend on this truck.

City and highway performance

The EPA estimates the Sierra Cab Chassis at 14 MPG in the city and 17 MPG on the highway. These figures reflect the realities of a heavy-duty drivetrain, a substantial curb weight even before a work body is installed, and the inherently inefficient nature of a large-displacement gasoline V8 engine. The 10-speed automatic transmission does its best to optimize the engine’s output, but ultimately, physics dictate the outcome. Stop-and-go city driving takes its toll, while highway cruising, even with some aerodynamic benefits, still requires a significant amount of power to maintain speed.

Annual fuel cost

The EPA estimates the annual fuel cost for the 2024 GMC Sierra Cab Chassis 4WD 5.3L 8-cyl at $2,900. This figure is based on driving 15,000 miles per year and using national average fuel prices. It’s a substantial amount, and fleet managers especially will need to factor this into their operating budgets. However, for the specific tasks this truck performs, and with the understanding that downtime is even more expensive, the fuel cost is often seen as a necessary expense. Check all Gmc fuel economy data here.

Real-world expectations

The EPA’s estimates provide a baseline, but real-world results will vary considerably. Payload, towing, weather conditions, and driving style all significantly influence fuel consumption. A Sierra Cab Chassis consistently loaded near its maximum GVWR will likely see even lower MPG figures. Conversely, a lightly loaded truck, driven conservatively, might occasionally approach the EPA’s highway estimate. However, consistently achieving or exceeding the EPA numbers is unlikely for most owners.

How it compares

Direct comparisons to other “trucks” become complicated quickly, as few vehicles share the Cab Chassis’s specific mission. A Ford F-350 DRW chassis cab with its 7.3L gas engine typically achieves similar fuel economy, perhaps one or two MPG better in combined driving. Ram’s equivalent 3500 chassis cab with its 6.4L Hemi V8 also posts similar fuel economy figures. These differences are small, and the buying decision hinges more on brand loyalty, upfitter compatibility, and specific features rather than a small amount of fuel savings. You’ll find more information on SIERRA MPG across all years here.

Tips to maximize efficiency

While the Sierra Cab Chassis isn’t designed for fuel efficiency, some practices can help optimize it. Avoid unnecessary idling. These large engines consume a surprising amount of fuel when idling, so shutting down the engine during extended stops can make a difference over time. For vocational applications that require extensive idling, explore auxiliary power units (APUs) as aftermarket upgrades; even a small APU can save hundreds of gallons per year.

Maintain proper tire inflation. Underinflated tires increase rolling resistance, forcing the engine to work harder. Check tire pressures regularly and inflate them to the manufacturer’s recommended specifications, considering the load being carried or towed.

Drive smoothly, avoiding hard acceleration and braking. This is especially important when carrying heavy loads. Anticipating traffic flow and maintaining a steady speed will minimize fuel waste. The 10-speed transmission is programmed to shift early and keep the engine in its most efficient range, so give it the space to do its work.

Service the vehicle according to the manufacturer’s recommendations. Regularly scheduled maintenance, including oil changes, air filter replacements, and tune-ups, ensures the engine is running optimally and efficiently. Don’t skip maintenance believing this will save money in the long run. It will only make things more expensive.