17 MPG combined isn’t a great figure for the 2018 GMC Sierra C15 2WD with the 6.2L V8. But those who choose this configuration aren’t prioritizing fuel savings. This Sierra is about power, responsiveness, and a certain swagger that only a big V8 in a light-duty truck can provide. It’s a workhorse dressed up for the weekend, and its owners happily pay the price at the pump for its capabilities.

City and highway performance

The EPA estimates for the 2018 GMC Sierra C15 2WD 6.2L are 15 MPG in the city and 21 MPG on the highway. The city figure reflects the engine’s thirst during stop-and-go driving, where its displacement and power become liabilities. The highway number is more palatable, benefiting from the eight-speed automatic transmission that allows the engine to cruise at lower RPMs. However, aggressive acceleration or hauling a heavy load will quickly diminish those highway gains.

Annual fuel cost

The EPA calculates the annual fuel cost for this Sierra configuration to be $3,400. 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. The calculation uses the national average fuel price at the time of the estimate. Remember that your actual fuel costs will vary depending on your driving habits, where you live, and prevailing gas prices. Someone who primarily uses this truck for short trips around town will likely exceed that $3,400 figure, while someone who does mostly highway miles may come in slightly under.

Real-world expectations

While the EPA provides a baseline, real-world fuel economy for the 2018 GMC Sierra C15 2WD 6.2L will vary widely based on individual driving styles and usage. Owners who frequently tow trailers, haul heavy payloads, or drive fast should expect figures closer to the city estimate, or even lower. Conversely, those who drive carefully on the highway, avoid excessive idling, and keep up with maintenance may see numbers closer to, or even slightly above, the EPA’s 21 MPG highway rating. Sturdy tires, aftermarket modifications, or neglecting routine service will also negatively impact fuel efficiency. Some owners average around 18 MPG in mixed driving, proving that the EPA’s combined figure is achievable with careful driving habits.

How it compares

Compared to other full-size trucks, the 2018 GMC Sierra C15 2WD 6.2L is predictably less fuel-efficient than models with smaller engines. For example, the 2.7L turbocharged four-cylinder in the Chevrolet Silverado offers a combined 20 MPG. Even Ford’s 2.7L EcoBoost V6 manages a combined 20 MPG in the F-150. The Ram 1500 with the eTorque mild-hybrid system also achieves better fuel economy with its V6 option.

Choosing the 6.2L V8 in the Sierra means trading fuel economy for the raw power and characteristic sound that many truck enthusiasts crave. For those who need a full-size truck, all Gmc fuel economy data will show that fuel economy improves when opting for a different engine. If you are looking for a lighter engine, compare SIERRA MPG across all years.

Tips to maximize efficiency

One of the easiest ways to improve the fuel economy of your 2018 GMC Sierra with the 6.2L engine is to be careful with your right foot; avoid fast acceleration and braking. Smooth, deliberate inputs will help you use less fuel. The 6.2L has plenty of torque, so there’s no need to constantly floor the accelerator.

Regular maintenance is also important. Make sure your tires are properly inflated to the recommended pressure. Check your air filter regularly and replace it when it’s dirty. A clean air filter allows the engine to breathe easier, improving fuel efficiency.

Consider using cruise control on the highway. Maintaining a consistent speed can significantly improve your highway fuel economy. However, avoid using cruise control in hilly terrain, as the transmission may downshift frequently, negating the benefits.

Avoid excessive idling. If you’re going to be stopped for more than a minute or two, turn off the engine. Idling consumes fuel without moving the vehicle. This is especially important with a large displacement engine like the 6.2L, which burns more fuel at idle than smaller engines.

Finally, consider using a fuel additive specifically designed to improve fuel economy. Some additives can help clean fuel injectors and improve combustion, resulting in better MPG. Look for reputable brands and follow the instructions carefully.