The Mercedes GLS is bought for space, but “seven seats” on a specification sheet is not enough to decide whether a particular car works for your family. Third-row access, luggage with all seats raised, child-seat placement, tyre cost and parking dimensions matter every week. Those are the areas that should drive an X166 versus X167 decision.
The X166 started life as the GL-Class and became GLS after the model-line renaming. The X167 is the newer generation with a more modern cabin and stronger emphasis on digital comfort. Both are large, heavy luxury SUVs, so the difference between a good used car and a neglected one can be expensive.
X166 vs X167 at a glance
| Factor | X166 | X167 |
|---|---|---|
| Purchase cost | Lower and more depreciated | Higher |
| Cabin technology | Older-generation interfaces | Newer MBUX-era displays and controls |
| Best reason to buy | Maximum space for less money | More modern three-row luxury experience |
| What to budget for | Age-related chassis and luxury-equipment work | High-cost tyres, brakes and option-dependent electronics |
Test the third row with the people who will use it
Put the second row in the position you actually use, then sit in the third row. Check access, knee room, headroom, vents, charging and cupholders. Load the luggage you would carry on a trip. A seven-seat SUV can still fail the household test if all seven seats leave too little usable cargo space.
If you rarely need the third row, compare a GLE before accepting the GLS’s larger footprint and running costs. The GLE W166 vs V167 guide covers that alternative.
Tyres, brakes and wheels can erase a bargain
Large wheels look appropriate on a GLS but make tyre replacement a serious budget item. Check brand, size, load rating, age and tread depth. Inspect rims for cracks, bends and poor cosmetic repair. During the test drive, feel for vibration under light steering input and through the seat.
Brake condition should be measured, not guessed. A low purchase price plus four tyres and substantial brake work may exceed the price of a cleaner car immediately.
Suspension is part of the purchase decision
Observe ride height when the vehicle has been standing. Operate height functions if fitted and watch for warning messages. Drive over uneven surfaces at low speed and listen for knocks or loose trim. Any repeated suspension warning requires a proper diagnostic inspection before purchase.
X166: value with age attached
The X166 can deliver an extraordinary amount of vehicle for the purchase price. The mistake is treating that depreciation as proof of cheap ownership. Inspect every powered seat, tailgate function, climate zone, camera, sunroof, lighting system and rear-seat feature. On an older flagship SUV, small neglected faults can accumulate.
A strong X166 is one with a believable maintenance record and evidence that expensive wear items were addressed when needed. A weak one is a car being sold just as several of those costs arrive together.
X167: buy the specification you actually need
The X167 cabin is more modern and can offer an impressive range of rear-seat comfort and assistance equipment. Do not pay for a generic “fully loaded” description. Confirm the exact options from the VIN and test them individually.
Because the X167 is newer, buyers sometimes skip a detailed inspection. That is a mistake. Collision repair, wheel damage, poor tyres and deferred service can affect a newer car just as easily as an older one.
Parking and daily use
Drive the car into a parking space similar to the one you use at home. Check camera clarity, sensor operation, mirror coverage and door-opening room. The GLS may be excellent on a family trip but frustrating if the owner is constantly worried about width in an urban garage.
Verdict
The X166 is the value route to a true large Mercedes SUV, provided the maintenance record is strong and the first-year budget is realistic. The X167 is the better choice when you genuinely use its newer technology and can absorb the higher purchase price without compromising inspection or maintenance.
Compare all Mercedes model sizes in the best used Mercedes-Benz guide, and use the pre-purchase inspection checklist before buying either generation.
Questions buyers ask about a used GLS
Can I judge a seven-seat SUV without bringing the family?
You can inspect it, but you cannot fully judge the packaging. Put the people who will use the third row into the car, fit the child seats and check luggage space with all required seats raised. That test can save an expensive change of vehicle later.
Does a newer X167 mean lower maintenance risk?
It reduces age, but not all risk. A newer car can still have collision repairs, damaged wheels, poor tyres or deferred maintenance. The X167 also has extensive electronics that should be tested before purchase.
What is the biggest budgeting mistake?
Comparing a depreciated GLS with a smaller new car only by purchase price. The GLS still uses large-SUV tyres, brakes and suspension. Estimate those costs before deciding the car is affordable.
Should I avoid an X166 with a towbar?
No. A towbar is information, not a verdict. Ask how the vehicle was used and inspect the installation, rear suspension and service history. Properly maintained towing use is different from unexplained heavy use.
