Mercedes GLS X167 used buyer’s guide: best year, engine and checks

The Mercedes GLS X167 used buyer’s guide most people need is short: buy the GLS 400d in AMG Line trim, with full Mercedes service history and a recent air-suspension check, and you get one of the calmest seven-seat luxury SUVs on the road for half its new price. Clean 2020 diesels now start around £45,000. We explain which year and engine to chase, what the air suspension and 48V system can cost, and the running numbers a UK buyer should budget before putting down a deposit. For context, our Mercedes S-Class W222 used buyer’s guide runs the comparable maths.

Which engine, trim and year to chase

The X167 GLS launched in the UK at the end of 2019 with a clear hierarchy. The GLS 400d uses Mercedes’ OM656 3.0-litre straight-six diesel making 330PS, the GLS 580 adds a 489PS M176 V8 petrol, and the headline acts are the Maybach GLS 600 and the 612PS Mercedes-AMG GLS 63. For the daily-driver UK buyer, the 400d is the one to chase: it pulls the 2.5-tonne body without strain, returns sensible motorway economy, and dominates the used classifieds. AMG Line is the trim to target for the bigger wheels and kit list most buyers want, with Premium and Premium Plus packs adding comfort and tech. On year, a late-2020 or 2021 car is the value sweet spot, while the April 2023 facelift (2024 model year) brought a four-louvre grille, revised lights and updated MBUX if you want the freshest look. Worth reading alongside our Mercedes GLC X253.

Cross-shopping a rival? Our BMW X7 G07 used buyer’s guide covers the GLS’s closest seven-seat competitor, and the smaller, cheaper Mercedes GLE W167 used buyer’s guide shares much of the same running gear if you do not need the third row in daily use.

What a clean X167 GLS costs in 2026

On an Auto Trader inventory scan dated 2 June 2026, clean 2020 GLS 400d AMG Line examples start at roughly £45,000 and run to around £59,000 depending on mileage and spec, with 2021 cars opening at about £46,000. Step up to a 2021 Mercedes-AMG GLS 63 and you are into the high £70,000s. Facelift 2024-model-year cars command a clear premium, so set your budget by year, not just by trim badge. Our view: a well-kept 2020 to 2021 400d at £45,000 to £55,000 is the strongest value, because the steepest depreciation has already happened and you still get the modern straight-six diesel, AIRMATIC and the full luxury cabin. The same exercise on the More CDE used premium buying guides arrives at a different answer.

Known faults and the checks to run before you pay

The X167 is solidly built, but it is a complex, heavy luxury SUV and the bills match. The single most important check is the AIRMATIC air suspension: on a test drive, confirm the car sits level, raises and lowers cleanly through the height modes, and has not sagged overnight. A tired compressor or leaking strut is a four-figure repair. Exercise the MBUX system, because owners report freezes and patchy updates. On 400d cars, look for a clean diesel particulate filter, especially on a car used only for short urban journeys. Insist on a full Mercedes-Benz main-dealer or specialist service history, and inspect tyres and brakes closely because replacements on 21 or 22-inch wheels are expensive. Finally, run the registration through the gov.uk DVSA vehicle-recall service: it shows no outstanding recalls for the GLS as of 2 June 2026, but a VIN check confirms the individual car. Some North American GLS recalls (a fuel-pump action and a 48V ground-cable inspection) were issued by the US NHTSA and do not appear on the UK DVSA record, so verify any imported car directly.

Running costs: insurance, tax and servicing

Budget honestly here. The GLS 400d AMG Line sits in insurance group 47 of 50 per Parkers’ Thatcham data, firmly in premium-SUV territory, so price up cover before you commit. Because every GLS cost well over £40,000 new, it carries the expensive-car VED supplement: for the current tax year that means the £200 standard rate plus the £440 supplement, a total of £640 a year from the second to the sixth time the car is taxed, per the gov.uk vehicle tax rate tables, before the rate drops back to the standard figure. Servicing is best covered by a Mercedes ServiceCare plan or a trusted independent, and main-dealer prices on a V8 580 are far higher than on the 400d. Add a tyre fund: a full set on the big AMG Line wheels runs into four figures. For a side-by-side, see our High-value car insurance over £50,000 in 2026.

The reliability picture, honestly

The X167 has no dominant catastrophic fault, which is the headline a used buyer wants. The concerns are age-related and predictable on a big, tech-laden Mercedes: air suspension, infotainment niggles and the cost of consumables. Parkers rates the GLS strongly as a luxury seven-seater while flagging that running costs are steep, and the lack of a model-wide DVSA safety recall on the cars we checked is a genuine positive, though you should still confirm the individual car by registration. The straight-six diesel in the 400d has a good durability reputation when serviced on time, another reason we steer most buyers towards it over the V8. The risk that flips our recommendation is paperwork: a GLS with gaps in its history or a neglected DPF can turn a £50,000 bargain into a money pit. Buy the car with the boring, complete service file.

Warranty and aftercare to line up

On a car this complex, cover is part of the buying decision, not an afterthought. A Mercedes-Benz Approved Used car comes with a manufacturer-backed warranty, the cleanest route to protect yourself on the air suspension and electronics; our BMW vs Audi vs Mercedes approved used warranty comparison sets out exactly what that cover does and does not include. If you buy privately or from an independent, read any aftermarket warranty’s wording on AIRMATIC and MBUX carefully, because those are the components most likely to fail and most likely to be excluded. We would rather pay a little more for a car with remaining manufacturer cover than gamble on a policy that walks away from the expensive parts.

Our take

This Mercedes GLS X167 used buyer’s guide lands on a confident recommendation: for most UK buyers the GLS 400d AMG Line, 2020 to 2021, at £45,000 to £55,000, with full Mercedes service history and a clean AIRMATIC check, is the car to buy. You get a serene, properly seven-seat luxury SUV for roughly half its new price, and the straight-six diesel is the engine we trust most for big-mileage ownership. The honest cons are real and worth weighing before you commit: insurance group 47, the £640 expensive-car VED years, four-figure tyres on the big AMG Line wheels, and the air-suspension risk that hangs over any ageing AIRMATIC car. The V8 580 and AMG 63 are wonderful but cost more to run than most owners expect, so reserve them for buyers who want the performance. The deal-breaker is paperwork: a GLS with gaps in its file or an undocumented suspension repair is one to walk away from, however tempting the screen price.