Mercedes-Benz GLS as a used car

The Mercedes-Benz GLS is one of the largest and most luxurious SUVs in the Mercedes-Benz range. Designed to combine the comfort of a luxury limousine with the practicality of a seven-seat family vehicle, it offers generous interior space, powerful engines, sophisticated technology and impressive long-distance capabilities. When purchased new, the GLS is an expensive vehicle, but depreciation has made older examples considerably more accessible on the used-car market. For buyers who need a spacious premium SUV and are prepared for the associated maintenance costs, a used GLS can be an attractive proposition.

However, buying a second-hand GLS requires more careful consideration than purchasing an ordinary family SUV. Its complex suspension, powerful engines, advanced electronics and extensive comfort equipment can all generate substantial repair bills as the vehicle ages. The condition of an individual car, its maintenance history and the way it has been driven are therefore particularly important. Understanding the differences between generations, knowing which engines are available and identifying potential weaknesses can help buyers find a GLS that delivers the luxury experience Mercedes originally intended.

Mercedes-Benz GLS generations: Which one should you buy?

Mercedes-Benz GLS X166 (2012–2019)

The first generation of the GLS was originally introduced as the GL-Class in 2012 and received the GLS designation following a facelift in 2015. Although the name changed, the basic vehicle remained the same, with updates to its appearance, interior equipment and powertrain range. The X166 was designed as a full-size luxury SUV, offering three rows of seats, a high driving position and a spacious cabin capable of accommodating larger families.

Today, the X166 is the more affordable way to enter GLS ownership. Its interior still feels substantial, particularly in well-equipped versions with leather upholstery, electrically adjustable seats, a panoramic sunroof and premium audio equipment. The driving experience focuses on comfort, with the suspension designed to absorb road imperfections and the powerful engines making motorway journeys effortless. However, buyers should remember that even the newest examples of this generation are now several years old, and expensive components may be approaching the end of their useful service life.

The facelifted GLS models are particularly interesting because they benefit from revised styling, updated technology and the nine-speed automatic transmission on many versions. Nevertheless, a well-maintained pre-facelift GL can also be worth considering if its condition and specification meet the buyer’s requirements.

Mercedes-Benz GLS X167 (2019 onwards)

The second generation, known internally as X167, arrived in 2019 and introduced a much more modern design, a larger and more refined cabin, and a new generation of digital technology. It retained the GLS’s characteristic three-row seating arrangement but improved passenger space and access to the rear seats. The interior adopted the Mercedes-Benz MBUX infotainment system, featuring large digital displays, voice controls and a more contemporary dashboard layout.

The X167 also introduced more advanced driver-assistance systems and sophisticated suspension technologies, depending on the model and equipment specification. Its combination of comfort, performance and technology makes it particularly appealing to buyers who want a modern luxury SUV without paying the price of a brand-new example. However, the more advanced systems also mean that repairs can be expensive, especially if the vehicle has been involved in an accident or has not received appropriate maintenance.

For buyers who intend to use all three rows regularly, the X167’s improved passenger accommodation can be a significant advantage. Its larger dimensions, however, also make parking and manoeuvring in narrow streets or older garages more challenging.

Engines: Which Mercedes-Benz GLS is the right choice?

Diesel engines for long-distance driving

Diesel engines are a natural fit for a vehicle as large and heavy as the GLS. Their strong torque at low engine speeds helps the SUV accelerate smoothly, even when fully occupied, while making it well suited to motorway journeys and towing. The X166 GLS 350 d, equipped with a 3.0-litre V6 diesel engine, is one of the familiar choices on the used market. It produces approximately 190 kW (258 hp) and offers substantial torque for everyday driving.

The newer X167 introduced Mercedes-Benz’s 2.9-litre inline-six diesel engines, including the GLS 350 d and GLS 400 d, with power outputs varying by model year and market. These engines provide refined performance and suit the character of the GLS particularly well. They are especially relevant to drivers who regularly cover long distances, where the diesel engine can operate under conditions that suit its emissions-control systems.

Nevertheless, used diesel GLS models require careful inspection. The diesel particulate filter, exhaust gas recirculation system and, where fitted, AdBlue equipment can all become sources of expensive repairs. Buyers should also check for oil leaks, unusual engine noises, inconsistent performance and evidence of neglected servicing. A vehicle used predominantly for short urban journeys may be less suitable than a higher-mileage example with a documented history of regular motorway driving.

Petrol engines for smoothness and performance

Petrol-powered GLS models are an alternative for buyers who prioritise quiet operation and smooth acceleration. The X166 range included V6 and V8 petrol engines, depending on the market, while the X167 introduced modern six-cylinder and V8 options with mild-hybrid assistance on many versions.

The GLS 450 is an appealing example of the petrol-powered approach, combining a six-cylinder engine with strong performance and refined operation. For drivers who want more power, the GLS 580 offers a 4.0-litre V8 in the newer generation. These engines provide effortless acceleration, although fuel consumption and the cost of maintaining a large petrol-powered SUV can be significant.

The AMG GLS 63 occupies a different category altogether. Its powerful V8 engine, sportier suspension tuning, distinctive styling and enhanced braking system make it a high-performance luxury SUV rather than simply a more powerful family vehicle. Used examples can be tempting as their initial purchase prices decline, but tyres, brakes, fuel and specialist servicing can make ownership considerably more expensive.

Reliability and common problems of a used GLS

Air suspension and chassis components

One of the most important systems to inspect on a used GLS is the AIRMATIC air suspension. It plays a major role in the vehicle’s comfort, helping to maintain a consistent ride height and adapting the suspension to different driving conditions. On some versions, more advanced active suspension systems are also available.

As the vehicle ages, air springs, seals, compressors and associated components can wear out or develop leaks. A GLS that sits unevenly after being parked overnight may have a suspension problem, although a proper diagnostic inspection is needed to establish the cause. During a test drive, listen for unusual knocking sounds and pay attention to excessive bouncing, uneven ride height or suspension warning messages. The X166 is particularly worth checking carefully because of its age and the weight it places on suspension components.

Engine, transmission and four-wheel drive

The engines fitted to the GLS are generally designed for substantial mileage, provided they receive the correct maintenance. However, a used vehicle may have experienced long service intervals, heavy towing or demanding driving conditions. On the older OM642 V6 diesel, for example, oil cooler seal leaks are a known inspection point. Other areas worth checking include the intake system, turbocharger-related components and emissions equipment.

The automatic transmission should also be inspected carefully. Most later GLS models use Mercedes-Benz’s nine-speed 9G-TRONIC automatic gearbox, while earlier examples may have a seven-speed transmission. Gear changes should be smooth and predictable, without harsh engagement, hesitation or unusual vibration. The 4MATIC all-wheel-drive system should be checked for abnormal noises, fluid leaks and evidence of neglected maintenance.

Electronics and interior equipment

The GLS offers a substantial amount of electrical and electronic equipment, especially in higher specifications. Electrically adjustable seats, multi-zone climate control, rear entertainment systems, parking cameras, electric tailgates and advanced driver-assistance features can all contribute to the luxury experience. However, every additional system represents another component that may require attention as the vehicle gets older.

Before buying, test all the equipment rather than assuming that a vehicle advertised as fully equipped is in perfect condition. Check the operation of the infotainment system, digital displays, cameras, parking sensors, seat adjustments, sunroof and rear climate controls. On the X167, pay particular attention to the MBUX system and any available active suspension features. A complete diagnostic scan can also reveal stored faults that may not be apparent during a short test drive.

Comfort, practicality and everyday driving

The GLS is designed primarily for comfort, and this is immediately apparent behind the steering wheel. Its elevated driving position provides excellent visibility, while the spacious cabin creates a relaxed atmosphere for both the driver and passengers. On long journeys, the comfortable seats, quiet interior and smooth automatic transmission make the GLS an excellent touring vehicle.

Its greatest practical advantage is the three-row seating arrangement. Unlike many SUVs that offer occasional third-row seats with limited usability, the GLS is designed to transport up to seven occupants. The third row is particularly useful for families with children or for occasional journeys with additional passengers. Nevertheless, the amount of luggage space available depends on whether the rear seats are folded or occupied, so buyers should check the exact configuration that suits their needs.

The large body also has disadvantages in everyday use. Narrow streets, underground car parks and tight parking spaces can become inconvenient, particularly for drivers who are not accustomed to large SUVs. The GLS is also a heavy vehicle, which places additional demands on its tyres, brakes and suspension. Its impressive towing capability can be useful, but the permitted trailer weight must always be checked against the specific vehicle’s documentation and equipment.

Maintenance costs and what to check before buying

A used GLS can offer a considerable amount of luxury for its depreciated purchase price, but maintenance costs remain those of a flagship Mercedes-Benz SUV. Routine servicing, premium tyres, brake components and replacement suspension parts can all be expensive compared with those of a smaller family vehicle. Powerful V8 and AMG versions generally require an even larger maintenance budget, particularly when they are fitted with large wheels and high-performance braking systems.

Before purchasing, it is worth obtaining a complete service history with invoices wherever possible. A professional pre-purchase inspection should cover the engine, transmission, suspension, brakes, steering, drivetrain and electrical systems. The vehicle should also be inspected for accident damage, corrosion, previous poor-quality repairs and fluid leaks. On diesel versions, a diagnostic check of the emissions-control system is particularly important.

Used Mercedes-Benz GLS pre-purchase checklist

• Verify the vehicle’s mileage and service history.
• Inspect the engine for leaks and unusual noises.
• Check the automatic transmission during cold and warm driving.
• Test the AIRMATIC or other fitted suspension system.
• Check the diesel emissions system, where applicable.
• Test all seats, climate controls, cameras and infotainment functions.
• Inspect the tyres, brakes and underside of the vehicle.
• Check for accident damage and outstanding recalls.
• Arrange an independent specialist inspection before purchase.

A particularly useful approach is to compare several examples rather than rushing to buy the cheapest one available. A vehicle with a higher asking price but a documented service history, recently replaced wear components and a clean diagnostic report may offer a more predictable ownership experience than a neglected example with impressive equipment.

Is the Mercedes-Benz GLS worth buying used?

The Mercedes-Benz GLS can be a highly practical choice for buyers who need a large, comfortable and luxurious seven-seat SUV. Its spacious interior, powerful engines, refined automatic transmission and impressive long-distance capabilities make it suitable for family travel, business use and towing. It also offers a level of passenger comfort and equipment that can be difficult to find in a conventional SUV at a similar used-car price.

The X166 is worth considering for buyers seeking a more affordable entry into flagship SUV ownership, provided they find a well-maintained example and budget for age-related repairs. The X167 is a more modern alternative, with improved technology, additional space and a more contemporary driving experience, although its purchase and repair costs can be higher.

Ultimately, the most important factor is the condition of the individual vehicle. A GLS with a complete service history, a healthy drivetrain and properly functioning suspension can provide many years of comfortable use. However, buyers should approach any example with deferred maintenance cautiously and retain sufficient funds for unexpected repairs. The GLS is not an inexpensive SUV to maintain, but for someone who genuinely needs its space, comfort and capabilities, it can be a rewarding used-car purchase.

Mercedes-Benz GLS technical specifications

The following table summarises representative specifications of the two GLS generations. Exact figures vary depending on the model year, engine, market and optional equipment. The current-generation figures are included as a reference and should not be confused with the specifications of earlier used examples.

Specifications are indicative and may differ by market, model year and trim. The official Mercedes-Benz specifications for the current GLS include a 5,217 mm length for selected diesel models, a 90-litre fuel tank and a 9G-TRONIC automatic transmission.