17 MPG combined isn’t going to win the 2020 GMC Sierra 4WD 4.3L 6-cyl any fuel economy awards, but that figure needs to be understood in the context of what this truck is: a workhorse. This Sierra configuration caters to buyers who prioritize capability and affordability over efficiency. It’s a practical choice for those needing a truck for hauling, towing, and navigating job sites, even if it means sacrificing some fuel savings at the pump.

City and highway performance

The EPA estimates a city MPG of 15 and a highway MPG of 20 for this Sierra configuration. The lower city rating reflects the stop-and-go driving and idling inherent in urban environments, conditions that penalize larger vehicles. The highway figure, while better, still lags behind smaller trucks and SUVs, owing to the Sierra’s weight and aerodynamic profile. The 6-speed automatic transmission, while reliable, lags behind newer 8- or 10-speed units in terms of efficiency, especially at higher speeds where more gears allow the engine to operate closer to its optimal RPM range. These numbers are considered acceptable by the target buyer, who prioritizes low-end torque and towing capacity over chasing every last mile per gallon. They know that the 4.3L V6, while not the most modern engine, is a known quantity with a reputation for durability. That often outweighs marginal fuel savings in the long run.

Annual fuel cost

The EPA estimates an annual fuel cost of $2,600 for the 2020 GMC Sierra 4WD 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, using national average fuel prices. Keep in mind that this is just an estimate. Your actual fuel costs will vary depending on your driving habits, the type of driving you do, and local fuel prices.

Even with this caveat, the $2,600 figure provides a useful benchmark for comparing the Sierra’s running costs against other trucks and understanding the potential financial impact of owning this configuration.

Real-world expectations

While the EPA estimates provide a standardized baseline, real-world fuel economy can vary significantly. Expect to see numbers slightly below the EPA estimates if you frequently tow heavy loads, drive aggressively, or spend a significant amount of time idling. Conversely, if you primarily use the Sierra for commuting on relatively flat highways and practice fuel-efficient driving techniques, you might achieve numbers closer to, or even slightly above, the EPA’s highway rating. Factors like tire pressure, vehicle maintenance, and even the type of fuel used can also influence your actual MPG. Consulting SIERRA MPG across all years can help you form your own expectations.

How it compares

Compared to other full-size trucks, the 2020 GMC Sierra 4WD 4.3L 6-cyl’s fuel economy places it near the lower end of the spectrum. For instance, a 2020 Ford F-150 with the 2.7L EcoBoost V6 engine achieves a combined MPG of around 22, translating to significant fuel cost savings over the course of a year. Even the Ram 1500 with the eTorque 3.6L V6 often sees closer to 20 MPG combined.

However, these more efficient powertrains often come at a higher initial purchase price, and buyers of the 4.3L Sierra may be willing to trade some fuel economy for a lower upfront cost and a simpler, more proven engine design. The Sierra’s fuel economy is comparable to, or even slightly better than, some older full-size trucks with larger V8 engines. For more information, browse all Gmc fuel economy data.

Tips to Maximize Efficiency

Consistent maintenance, including regular oil changes and air filter replacements, can improve the engine’s overall efficiency. A well-maintained engine runs smoother and requires less fuel to operate, so don’t skip scheduled services.

Minimize idling whenever possible. Letting the engine run unnecessarily wastes fuel. If you’re going to be stopped for more than a minute or two, it’s generally more efficient to turn off the engine and restart it.

Check your tire pressure regularly and maintain the recommended inflation levels. Underinflated tires increase rolling resistance, which reduces fuel economy. The correct tire pressure is listed on a sticker inside the driver’s side door jamb.

Avoid aggressive driving habits, such as rapid acceleration and hard braking. These actions consume more fuel. Smooth, gradual acceleration and anticipation of traffic conditions can significantly improve your MPG.

Consider using cruise control on the highway. Maintaining a consistent speed can help optimize fuel economy, especially on long trips. Just be mindful of traffic conditions and adjust your speed accordingly.