17 MPG combined is a stark reality for buyers considering the 2020 GMC Sierra Cab Chassis 2WD with the 4.3L V6. This isn’t a grocery-getter or a family hauler; it’s a work truck designed to be upfitted with everything from utility bodies, to service beds, to stake sides. Fuel economy is a consideration, certainly, but payload and capability are the primary drivers for those who sign on the dotted line.

City and highway performance

The EPA estimates suggest 15 MPG in the city and 19 MPG on the highway. These numbers reflect the engine’s inherent design. The 4.3L V6 is a durable, simple engine designed to provide adequate power for moderate workloads. It’s not built for blistering acceleration or maximizing fuel efficiency. Stop-and-go city driving will always be its achilles heel, while highway cruising, assuming moderate speeds, will provide the best possible fuel economy, especially when the vehicle is unladen or lightly loaded. Realistically, however, very few of these Cab Chassis trucks spend much time traveling empty; they’re usually laden with tools, equipment, or materials.

Annual fuel cost

The EPA estimates an annual fuel cost of $2,600 for the 2020 GMC Sierra Cab Chassis 2WD 4.3L 6-cyl. This figure is based on driving 15,000 miles per year, with 55% of those miles driven in the city and 45% on the highway. It also assumes national average fuel prices. Remember that your actual fuel costs will vary depending on how and where you drive, and of course, the ever-changing price of gasoline. Operators of these trucks, who often use them for commercial purposes, should meticulously track fuel costs to understand their operating expenses and potentially identify areas for improvement in driver behavior or route optimization.

Real-world expectations

Don’t expect to consistently achieve the EPA’s numbers in real-world use. These trucks are frequently subjected to heavy loads, idling at job sites, and driving in congested areas. All those factors drag down average MPG. A more realistic expectation for combined fuel economy is probably closer to 14-16 MPG, maybe even lower depending on the type of upfit and the typical workload. Owners often report that they don’t prioritize miles per gallon in this sector, the truck is an investment in their livelihood, and the cost of doing business includes fuel. It’s also why you should review all Gmc fuel economy data when making purchasing decisions.

How it compares

The 2020 Sierra Cab Chassis faces limited direct competition, particularly when considering the specific 4.3L V6 configuration and 2WD drivetrain. Comparing it to other full-size trucks can be insightful, though, especially if considering alternative engine choices. For example, a comparably equipped 2020 Ford F-150 XL with the 3.3L V6 and 2WD achieves a slightly better 20 MPG combined. However, the F-150 typically isn’t configured as a Cab Chassis model from the factory. If you were to compare the same 4.3 V6 to other SIERRA MPG across all years, it will be quite similar. The Ram 1500 Classic Tradesman with the 3.6L V6 and 2WD also offers a better fuel economy of of 19 MPG combined. These MPG differences might seem significant, but for buyers in the Cab Chassis segment, upfront cost, payload capacity, and upfitting compatibility often outweigh minor fuel economy advantages. The focus is on getting the job done, not setting fuel efficiency records. So you need to look at SIERRA MPG across all years to know what to expect.

Tips to maximize efficiency

Driving habits have an outsized effect on fuel economy in a vehicle of this type. Avoid aggressive acceleration and hard braking. Plan your routes to minimize stop-and-go driving and avoid rush-hour congestion whenever possible. Every unnecessary acceleration event burns more fuel than you realize.

Proper tire inflation is critical. Check your tire pressure regularly and maintain the recommended pressure listed on the door jamb. Underinflated tires increase rolling resistance, which directly reduces fuel economy. This is even more important when the truck is carrying a load.

Minimize idling. Idling consumes fuel without covering any distance. If you anticipate being stationary for more than a minute or two, turn off the engine. Many newer vehicles have automatic start/stop systems, but this 2020 Sierra configuration likely does not. Be proactive about shutting it down manually.

Reduce unnecessary weight. The heavier the load, the more fuel the engine consumes. Remove any tools or equipment that you don’t need for the current job. Less weight translates directly into improved fuel economy, however marginal. It also improves braking performance.

Consider using cruise control on the highway where appropriate. Maintaining a constant speed can help optimize fuel economy on long stretches of open road. Be mindful of traffic conditions and avoid excessive use of cruise control in hilly areas where the transmission may downshift frequently.