17 MPG combined is the figure associated with the 2015 GMC Sierra K15 4WD 6.2L 8-cyl. It’s a reminder that you’re driving a serious piece of machinery, not a fuel-sipping commuter. This truck isn’t for everyone, and GMC knows it. Buyers of the 6.2L Sierra aren’t prioritizing fuel efficiency above all else. They’re after capability and V8 power. They need to tow heavy loads, handle challenging terrain, and show strength, and they’re willing to pay more at the pump for it. This Sierra configuration is for a specific buyer: the contractor hauling equipment, the weekend warrior towing a boat or camper, or someone who prefers the commanding presence and power that this engine provides. It’s about getting the job done, and looking good doing it.

City and highway performance

The EPA estimates 15 MPG in the city and 21 MPG on the highway for this Sierra. The city figure shows the inefficiencies of stop-and-go driving, made worse by the engine’s size and the truck’s weight. Expect fuel consumption to increase in urban environments. On the open road, the 8-speed automatic transmission helps the 6.2L settle into a more efficient cruise, resulting in near-estimated highway MPG. However, even minor inclines or headwinds can lower that number. These figures are based on ideal conditions. Aggressive acceleration, towing, or larger tires will reduce both city and highway MPG.

Annual fuel cost

According to the EPA, the annual fuel cost for the 2015 GMC Sierra K15 4WD 6.2L 8-cyl is about $2,600. This figure is based on driving 15,000 miles per year, using a mix of city and highway driving, and average fuel prices. This is only an estimate, and your actual fuel costs may vary depending on your driving habits, local fuel prices, and how you use the truck. If you primarily use the Sierra for heavy towing, expect to spend more than $2,600 per year on fuel. This is a large number, especially when compared to all Gmc fuel economy data for their lineup, but that rarely sways those committed to the 6.2L engine.

Real-world expectations

The EPA estimates provide a baseline, but real-world fuel economy often differs. Expect to see numbers slightly below the official ratings, particularly in mixed driving conditions. Many owners report average fuel economy in the 14-18 MPG range, depending on driving style and usage. Towing, hauling heavy loads, frequent short trips, and aggressive driving habits will impact fuel consumption. Using cruise control on flat highways can help you get closer to the EPA’s highway estimate. Understanding your driving patterns and being mindful of fuel-efficient driving techniques can help you manage your fuel costs.

How it compares

Consider the Sierra’s fuel economy in the context of its competitors. The Ford F-150 with its available 5.0L V8 engine achieves around 19 MPG combined in 4×4 configuration, offering a slight edge. Ram’s 1500 with the 5.7L HEMI V8 sees similar figures to the F-150. However, if you look at Chevy’s lineup and the SIERRA MPG across all years to the newer versions of the Sierra, you might be able to find an older model that nets you better fuel economy. The Toyota Tundra, known for its reliability but not its fuel efficiency, struggles to break 16 MPG combined with its 5.7L V8. The Sierra’s 6.2L offers power and torque, but its fuel economy lags behind some competitors. Buyers choosing the 6.2L are often prioritizing power over fuel efficiency, accepting the trade-off for the engine’s capabilities and performance.

Tips to maximize efficiency

Avoid sudden acceleration and hard braking. The 6.2L engine, with its torque, doesn’t need to be pushed hard to get up to speed. Gentle acceleration preserves fuel and reduces wear and tear. Keep a consistent speed whenever possible. The 8-speed transmission will automatically downshift if it detects a need for the engine to take over.

Tire inflation is critical. Check your tire pressure regularly and keep it at the recommended level, found on the driver’s side doorjamb. Underinflated tires increase rolling resistance, which hurts fuel economy. Make sure your tires are the appropriate size for the vehicle and do not alter the engine’s or truck’s mechanics to accommodate different tire sizes.

Minimize idling. Idling consumes fuel. If you’re stopped for more than a minute or two, turn off the engine. Modern engines are designed to restart quickly and efficiently, so there’s no need to let the engine run unnecessarily.

Remove extra weight. Extra weight places strain on the engine and reduces fuel economy. Remove any unnecessary cargo from the bed of the truck, and only carry what you need.