Mercedes GLS Fuel Economy Test: Effortless Power

Mercedes GLS fuel economy tests reveal that its “effortless power” can be surprisingly efficient, balancing robust performance with practical mileage when driven intelligently. Expect competitive MPG figures for its class.

The Mercedes-Benz GLS is often seen as the pinnacle of luxury SUVs, a spacious, powerful, and supremely comfortable vehicle. But for many owners and prospective buyers, a significant question lingers: how does this mighty machine handle fuel consumption? It’s a common concern, especially with large, premium SUVs, and finding clear, reliable information can feel challenging. You want to understand the real-world MPG, not just the manufacturer’s claims. At MercedesBlue, we’re here to demystify the Mercedes GLS fuel economy test, separating hype from reality and ensuring you feel confident about what to expect. We’ll dive into the factors influencing its mileage and what you can do to maximize it.

Understanding Mercedes GLS Fuel Economy: The Big Picture

The Mercedes-Benz GLS is a full-size luxury SUV designed to offer ample space for up to seven passengers, sophisticated technology, and the commanding presence synonymous with the Mercedes-Benz brand. Its robust performance, especially from the potent V8 engines typically found under the hood (or the inline-six in some configurations), naturally leads many to assume it guzzles fuel. However, modern engineering has made significant strides in improving efficiency, even in vehicles of this caliber. We’ll explore just how efficient the GLS can be, considering its size and power output.

Factors Affecting GLS Fuel Economy

Several elements play a crucial role in determining the actual miles per gallon (MPG) you’ll achieve with your Mercedes GLS. Understanding these will help you interpret test results and manage your own driving habits for better efficiency.

• Engine Choice: The GLS has offered various engine options over the years, from more efficient inline-sixes to powerful V8s. The number of cylinders, displacement, and any performance enhancements (like turbocharging or mild-hybrid systems) directly impact fuel consumption.
• Driving Conditions: City driving, with its frequent stops and starts, will always yield lower MPG than highway cruising. Conversely, aggressive acceleration and hard braking on the highway also deplete fuel faster.
• Driver Behavior: Your right foot is a significant factor. Smooth acceleration, anticipating traffic, and maintaining a steady speed are key.
• Vehicle Load: Carrying passengers or cargo adds weight, which requires more energy (and thus fuel) to move.
• Tire Pressure: Underinflated tires increase rolling resistance, forcing the engine to work harder and consume more fuel. Regularly checking and maintaining proper tire pressure is crucial. You can find the recommended PSI on a sticker in your driver’s side doorjamb or in your owner’s manual.
• Maintenance: A well-maintained vehicle runs more efficiently. This includes regular oil changes, air filter replacements, and ensuring the engine is in optimal condition.
• Aerodynamics: While less impactful than engine or driving style, factors like roof racks or open windows at high speeds can slightly increase drag and thus fuel usage.

Mercedes GLS Fuel Economy Test: EPA Estimates vs. Real World

Official fuel economy ratings, primarily from the Environmental Protection Agency (EPA) in the US, provide a standardized benchmark. These tests are conducted under controlled conditions to allow for consistent comparisons between different vehicles. However, they don’t always perfectly reflect everyday driving scenarios. Let’s look at typical EPA estimates for recent Mercedes-Benz GLS models.

Note: Fuel economy figures can vary significantly based on the specific model year, engine variant (e.g., GLS 450, GLS 580, AMG GLS 63), and drivetrain (RWD vs. 4MATIC AWD, though most GLS models are AWD). The numbers below are representative examples and should be cross-referenced with specific model year data for accuracy.

EPA Fuel Economy Estimates (Representative Examples)

Here’s a look at what you might expect from the EPA for common GLS configurations:

Model	Engine	Drivetrain	City MPG (Est.)	Highway MPG (Est.)	Combined MPG (Est.)
GLS 450 4MATIC (Recent Model)	3.0L Turbo I6 with Mild Hybrid	AWD	19 MPG	23 MPG	21 MPG
GLS 580 4MATIC (Recent Model)	4.0L Twin-Turbo V8 with Mild Hybrid	AWD	18 MPG	22 MPG	20 MPG
AMG GLS 63 4MATIC+ (Performance Model)	4.0L Twin-Turbo V8	AWD	15 MPG	19 MPG	17 MPG

As you can see, even the more powerful V8 engines, when equipped with mild-hybrid technology (often denoted by EQ Boost), offer surprisingly competitive figures for a vehicle of this size and capability. The AMG GLS 63, as expected for a high-performance variant, prioritizes power over economy, but its figures are still within a reasonable range for its class.

Real-World MPG: What Drivers Experience

While EPA estimates are helpful, real-world driving conditions are the ultimate test. Many GLS owners report that achieving the combined MPG is attainable with a mix of city and highway driving. However, pushing the vehicle hard, heavy acceleration, or extensive city commuting can lead to lower numbers, sometimes dipping a few MPG below the estimates. Conversely, consistent highway cruising at moderate speeds can sometimes exceed the highway MPG ratings.

For instance, a common observation for the GLS 450 is achieving around 20-22 MPG on highways and 17-19 MPG in combined city/highway driving. For the GLS 580, this might look like 19-21 MPG on the highway and 16-18 MPG combined. The AMG GLS 63 owners often report figures closer to 15-17 MPG combined, especially when its performance is utilized.

How to Improve Your Mercedes GLS Fuel Economy

Regardless of the specific GLS model you own or are considering, there are practical strategies you can employ to maximize your fuel efficiency. These aren’t complex modifications but rather smart driving and maintenance habits.

Driving Techniques for Better MPG

Your driving style has a profound impact on fuel consumption. Here’s how to drive more efficiently:

• Smooth Acceleration and Braking: Avoid sudden bursts of speed and hard braking. Accelerate gently and anticipate when you need to slow down, allowing the vehicle to coast.
• Maintain a Steady Speed: On the highway, cruise control is your friend. Keeping your speed consistent helps the engine operate at its most efficient RPM.
• Observe Speed Limits: Fuel economy typically drops significantly when exceeding 50-60 mph. Driving faster on the highway consumes considerably more fuel.
• Minimize Idling: If you’re going to be stopped for more than a minute, it’s generally more efficient to turn off the engine. This is especially relevant for the GLS’s mild-hybrid system, which can shut off the engine in certain situations when stopped.
• Plan Your Routes: Combine errands to avoid multiple cold starts and short trips, as engines are less efficient when cold. Using navigation that accounts for traffic can also help you avoid congested areas.

Vehicle Maintenance for Optimal Efficiency

A well-maintained GLS runs more efficiently and reliably. Key maintenance tasks include:

• Regular Oil Changes: Use the manufacturer-recommended oil viscosity for your engine. Clean, fresh oil lubricates better, reducing friction and improving efficiency. Consult your owner’s manual or a trusted Mercedes-Benz service center for the correct oil type and change intervals.
• Air Filter Replacement: A clogged air filter restricts airflow to the engine, making it work harder and burn more fuel. Check and replace it according to the maintenance schedule.
• Tire Pressure Checks: As mentioned, properly inflated tires are critical. The National Highway Traffic Safety Administration (NHTSA) emphasizes the importance of correct tire inflation for safety and fuel economy.
• Wheel Alignment: Misaligned wheels can increase tire wear and rolling resistance, negatively impacting fuel economy.
• Spark Plug Replacement: Worn spark plugs can lead to incomplete combustion, reducing engine performance and efficiency.

Leveraging Mercedes-Benz Technology

The GLS is equipped with advanced technologies designed to enhance performance and efficiency.

• Eco Mode: Selecting the “Eco” driving mode (if available on your model) adjusts throttle response, transmission shift points, and climate control settings to prioritize fuel savings.
• Start/Stop System: Modern GLS models with mild-hybrid technology (EQ Boost) feature an automatic engine start/stop system that shuts down the engine when the vehicle is stationary and restarts it seamlessly when you’re ready to move.
• Active Distance Assist DISTRONIC: Mercedes-Benz’s advanced adaptive cruise control can help maintain a set speed and distance from the vehicle ahead, often leading to smoother driving and improved fuel economy on the highway.

Mercedes GLS 450 Fuel Economy: Efficient Power

The GLS 450 often serves as the entry point into the GLS lineup, typically featuring a 3.0-liter turbocharged inline-six engine paired with Mercedes-Benz’s EQ Boost mild-hybrid system. This combination is designed to deliver strong performance while being more fuel-conscious than traditional V8s.

Key Features of the GLS 450’s Powertrain:

• Inline-Six Engine: Known for its inherent smoothness and efficiency.
• Turbocharging: Provides ample power when needed.
• EQ Boost Mild-Hybrid System: A starter-generator that provides a temporary power boost, assists with regenerative braking, and allows for smoother, more frequent engine shut-offs by the ECO Start/Stop system.

When tested, the GLS 450 (recent models) generally achieves EPA estimates around 19 MPG city, 23 MPG highway, and 21 MPG combined. In real-world driving, many owners report seeing closer to 17-19 MPG in mixed driving and up to 23-25 MPG on the highway, especially if driving conditions are favorable and driving habits are conservative. This makes the GLS 450 a compelling option for those who want luxury and space without an excessive fuel bill.

Mercedes GLS 580 Fuel Economy: V8 Muscle Meets Efficiency

Stepping up to the GLS 580 brings a 4.0-liter twin-turbocharged V8 engine, also typically equipped with the EQ Boost mild-hybrid system. This powerplant offers significantly more horsepower and torque, providing a more exhilarating driving experience.

Performance Highlights of the GLS 580:

• Twin-Turbo V8: Delivers potent acceleration and a substantial feeling of power.
• EQ Boost Integration: Helps mitigate some of the inherent thirst of a V8, improves responsiveness, and aids in efficiency features like smoother start/stop.

The EPA estimates for the GLS 580 often hover around 18 MPG city, 22 MPG highway, and 20 MPG combined. Real-world results tend to align closely, with drivers reporting combined figures between 16-18 MPG and highway figures potentially reaching 20-22 MPG under ideal conditions. While slightly less efficient than the GLS 450, the GLS 580 offers a significant performance upgrade that many find worth the trade-off in fuel economy, especially considering the advanced hybrid assistance.

AMG GLS 63 Fuel Economy: Performance First

For the ultimate in performance, the AMG GLS 63 commands attention. It features a hand-built AMG 4.0-liter V8 biturbo engine, tuned for maximum power output. Fuel economy is naturally a secondary consideration here, but the engineering is still remarkable.

AMG GLS 63: Power Uncompromised

• High-Output AMG V8: Engineered for exhilarating acceleration and a dynamic driving experience.
• AMG SPEEDSHIFT TCT Transmission: Optimized for performance delivery.

As expected, the AMG GLS 63’s fuel economy figures are lower. EPA estimates are typically around 15 MPG city, 19 MPG highway, and 17 MPG combined. Real-world figures often fall within the 14-16 MPG range for mixed driving, reflecting the engine’s performance-oriented nature. Enthusiasts opting for the AMG GLS 63 understand that this is a trade-off for uncompromising power and the signature AMG driving sensation.

Comparing GLS Fuel Economy Across Generations

It’s worth noting that fuel economy has improved across generations of the Mercedes-Benz GLS (and its predecessor, the GL-Class). Newer models, particularly those incorporating mild-hybrid technology and more advanced engine management systems, generally offer better efficiency than older, naturally aspirated or less technologically advanced turbocharged engines, even when comparing vehicles with similar displacement.

For example, an older GL 550 with a standard V8 might have had EPA combined ratings in the mid-teens, whereas a modern GLS 580 achieves closer to 20 MPG combined. This evolution is a testament to ongoing advancements in automotive engineering aimed at balancing performance with environmental responsibility and cost of ownership.

Frequently Asked Questions (FAQ)

Q1: What is the best MPG Mercedes GLS model?

The Mercedes GLS 450, equipped with the 3.0L turbocharged inline-six and EQ Boost mild-hybrid system, generally offers the best fuel economy among the GLS lineup, with EPA estimates typically around 21 MPG combined.

Q2: Does the GLS 580 use a lot of gas?

The GLS 580, with its V8 engine, is less fuel-efficient than the GLS 450. However, its EPA combined estimate of around 20 MPG is considered competitive for a large, powerful luxury SUV, especially when considering its performance and the assistance provided by the mild-hybrid system.

Q3: How does the mild-hybrid (EQ Boost) system affect fuel economy?

The EQ Boost system adds a small electric motor/generator that can provide temporary power assistance, allow the engine to shut off more frequently when coasting or stopped, and recapture energy during braking (regenerative braking). These functions contribute to improved fuel efficiency compared to non-hybrid V8 or inline-six engines in similar vehicles.

Q4: Can I improve my GLS’s MPG significantly?

Yes, by adopting efficient driving techniques (smooth acceleration, steady speeds, anticipating traffic) and ensuring proper vehicle maintenance (tire pressure, air filter, oil changes), you can noticeably improve your GLS’s fuel economy. Utilizing the vehicle’s Eco mode and adaptive cruise control can also help.

Q5: Are the AMG GLS 63 fuel economy figures accurate?

The EPA figures for the AMG GLS 63 (around 17 MPG combined) are estimates. Actual mileage can vary significantly, often being lower if the potent performance is frequently accessed. Owners of performance vehicles like the AMG GLS 63 generally prioritize power over absolute fuel efficiency.

Q6: How does driving in the city vs. highway affect GLS MPG?

City driving, with its stop-and-go traffic, requires more fuel and will result in lower MPG compared to highway driving. The GLS’s start/stop system and mild-hybrid technology help to mitigate some of this inefficiency, but highway cruising remains the most fuel-efficient driving scenario for any vehicle. You can expect highway MPG to be notably higher than city MPG.

Conclusion

The Mercedes-Benz GLS is a remarkable achievement in automotive engineering, offering a harmonious blend of luxury, space, and dynamic performance. When it comes to fuel economy, the GLS proves that “effortless power” doesn’t necessarily mean excessive consumption. While it’s a full-size luxury SUV, its modern powertrains, including efficient inline-six and V8 engines paired with mild-hybrid technology, deliver competitive MPG figures for its class. The GLS 450 stands out as the most fuel-conscious option, while the GLS 580 provides a potent V8 experience with respectable efficiency, and the AMG GLS 63 offers uncompromised performance for those who demand it.

By understanding the factors that influence fuel consumption and adopting smart driving habits and diligent maintenance practices, GLS owners can optimize their vehicle’s efficiency. Whether you’re comparing models before purchase or seeking to get the most out of your current GLS, this deep dive into its fuel economy should provide clarity and confidence. The Mercedes-Benz GLS continues to redefine what’s possible in the realm of luxury SUVs, proving that power and practicality can indeed go hand-in-hand.