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Mercedes-Benz · Full-Size SUV · 2012–2019

Mercedes-Benz GLS X166

Weaknesses, engine ratings and buying advice

★★★★★
1.5 / 5.0 · Based on 4 engine variants
Most Fun Engine

525–585 PS

5.5L V8 BiTurbo Benzin

585 hp Full-Size SUV — 7 Seats and Motorway Dominance

Fun to Drive!
Problem Engine

408–455 PS

4.7L V8 BiTurbo Benzin

9 weaknesses

Stay Away!

Generations

Engine Overview

The Mercedes-Benz GLS X166 is available with 4 engine variants — from 190 to 585 hp.

GL 350 BlueTEC · Diesel· 258 PS
2012 2019
Stay Away! 7 weaknesses
Show all weaknesses →
AMG GLS 63 · Benziner· 585 PS
2015 2019
Stay Away! 11 weaknesses
Show all weaknesses →
GLS 400 · Benziner· 333 PS
2015 2019
Be Careful 10 weaknesses
Show all weaknesses →
GLS 500 · Benziner· 455 PS
2015 2019
Stay Away! 9 weaknesses
Show all weaknesses →

The Mercedes-Benz GL 350 BlueTEC (Diesel, 258 PS) has the OM642 (3.0L V6 Diesel) — rated: "Stay Away!", 7 known weaknesses.

The Mercedes-Benz AMG GLS 63 (Benziner, 585 PS) has the M157 (5.5L V8 BiTurbo) — rated: "Stay Away!", 11 known weaknesses.

The Mercedes-Benz GLS 400 (Benziner, 333 PS) has the M276 (3.0-3.5L V6) — rated: "Be Careful", 10 known weaknesses.

The Mercedes-Benz GLS 500 (Benziner, 455 PS) has the M278 (4.7L V8 BiTurbo) — rated: "Stay Away!", 9 known weaknesses.

Vehicle Weaknesses

WeaknessCost
✖Airmatic air springs and compressor defective

Airmatic air springs become porous and lose pressure. The compressor runs continuously, overheats and fails. High-pressure lines can show damage from as early as 38,000 km.

Symptoms: Vehicle sits lower or lopsided, Airmatic warning, hissing noise, compressor running continuously
from 130,000 km
Ad air strut GLS X166 rearAirmatic supercharger X166
 High
!AIRMATIC Air Bellows Porous

Air bellows become porous and lose pressure. High-pressure lines can chafe through. Repair 400–2,500 EUR.

Symptoms: Vehicle sags, AIRMATIC fault message, compressor runs long, unusually harsh ride.
from 90,000 km
Ad A1663200425 GLS X166 air spring
 High
NHTSA Owner Complaints
Below Average
216 complaints · 2012–2019
Engine
45 ⚠ 1
Airbags
43 ⚠ 3
Electrical
25
Other
22
Brakes
19 ⚠ 2

Top Reported Issues

⚠ Engine (45 complaints)
⚠ Airbags (43 complaints)
⚠ Electrical (25 complaints)
Source: NHTSA (nhtsa.gov) · 2026-03

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Known Problems and Issues

A total of 43 weaknesses have been documented for the Mercedes-Benz GLS X166 (2012–2019) — 37 engine-related and 6 vehicle-related. 3 problem engines: OM642 (3.0L V6 Diesel), M157 (5.5L V8 BiTurbo), M278 (4.7L V8 BiTurbo). Typical issues affect Suspension, Gearbox, Electronics, Brakes.

GLS (OM642, 2012–2019) — Stay Away!: Oil Cooler Gaskets Leaking — Oil and Coolant Loss, Swirl Flap Linkage Breaks — Plastic Joint Fails, Injector Seal Leaking — Soot Deposits and Diesel in Oil. Power: 258 PS.

GLS (M276, 2015–2019) — Be Careful: Oil cooler leaking in the V-block, Camshaft adjuster leaking — wiring harness contaminated, Piston slap (early 3.5L variants). Power: 333 PS.

GLS (M157, 2015–2019) — Stay Away!: Timing Chain Stretch — M157 BiTurbo V8, Oil Consumption from Piston Ring Wear, High-Pressure Fuel Pump Fails — No Fuel Pressure. Power: 585 PS.

GLS (M278, 2015–2019) — Stay Away!: Timing chain tensioner failure (early production), Cylinder bore scoring (Silitec coating), Camshaft adjuster solenoid — oil destroys ECU. Power: 455 PS.

What to watch out for with the Mercedes-Benz GLS? See the detailed listing of all engine and vehicle weaknesses in the sections above.

Frequently Asked Questions

What problems and weaknesses does the Mercedes-Benz GLS X166 have? +
The Mercedes-Benz GLS X166 has 37 known engine weaknesses and 6 vehicle weaknesses.
What should I look for when buying a used Mercedes-Benz GLS X166? +
faq.watch_a_avoid
Which engine is recommended? +
Be careful: M276 (3.0-3.5L V6). No engine is rated 'Good Choice'. The most fun to drive is the M157 (5.5L V8 BiTurbo). Problem engine: M278 (4.7L V8 BiTurbo) — stay away!
Which Mercedes-Benz GLS X166 engine is the most fun? +
The {code} ({displacement}) offers the most driving fun in the Mercedes-Benz GLS X166 — rated: "Fun to Drive!". {description} GLS 63 AMG: 585 hp V8 BiTurbo in the largest Mercedes SUV. 2.6 tonnes, 7 seats, 0–100 in 4.6 seconds — pure absurdity. The M157 does its most impressive work here: a turbocharged engine that delivers 760 Nm early and broadly to make 2.6 tonnes enjoyable. For large families who refuse to compromise on anything. Car park nightmare included.
Is the Mercedes-Benz GLS X166 worth buying used? +
Caution is advised with the Mercedes-Benz GLS X166 — 3 of 4 engine variants are rated 'Stay Away!'. The engine choice is crucial.
What horsepower variants are available for the Mercedes-Benz GLS X166? +
The Mercedes-Benz GLS X166 is available with engine variants from 190 to 585 hp. Petrol: M276 (3.0-3.5L V6), M157 (5.5L V8 BiTurbo), M278 (4.7L V8 BiTurbo). Diesel: OM642 (3.0L V6 Diesel).

Last updated: February 2026 · All information without guarantee