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Mercedes-Benz GLS X166 (GL/GLS) (2013-2019) reliability

At a glance

Mercedes-Benz GLS X166 (GL/GLS) built around 2018: more dangerous faults than average

Testers find a dangerous fault on Mercedes-Benz GLS X166 (GL/GLS) models built around 2018 more often than on similar cars the same age. Look closely at the tyres on any car you view.

Looking at a Mercedes-Benz GLS X166 (GL/GLS) right now?

Enter its number plate to see its full MOT history, risk rating and running costs.

Key figure

7% of MOT tests on Mercedes-Benz GLS X166 (GL/GLS) models built around 2018 found a fault the tester marked as dangerous, against 5% for similar cars the same age.

Most common issue

The most common MOT issue on Mercedes-Benz GLS X166 (GL/GLS) models built around 2018 involves the tyres.

No reliability rating: not enough tests to rate2013-2019SUVDIESEL / PETROL

Based on 2,140 tests of GLS models registered 2013-2019.

About 1 in 30 GLS X166 (GL/GLS) MOTs (3.5%) failed and still hadn't passed 3 days later. That's for cars built around 2018 (7 years old), all fuels combined.

Based on 620 tests (DVSA MOT results, 2025), a small sample, so the figure is likely between 2.4% and 5.3%. A fail that passed a retest within 3 days, even the same day, isn't counted. Nor is a fail with no later MOT on record.

About 1 in 15 GLS X166 (GL/GLS) MOTs (6.8%) found at least one dangerous defect. These are cars built around 2018 (7 years old).

Based on 620 tests (DVSA MOT results, 2025), a small sample, so the figure is likely between 5.1% and 9.0%. Dangerous is the most serious grade an MOT gives: a direct risk to road safety.

X166 (GL/GLS) fail rate by age

Below typicalAbove typicalHigh (28% or more)Highest fail rateUK average for cars this age
Age / builtFail rateMOT tests
5 yearsbuilt around 2020
16313.5%
6 yearsbuilt around 2019
54611.9%
7 yearsbuilt around 2018
62011.6%
8 yearsbuilt around 2017
61310.0%
9 yearsbuilt around 2016
19815.7%

Fail rate is the share of MOT tests that ended in a fail. Retests count as tests. How we count fail rates Build years are worked out from age, so they are approximate. Tests counted are 2025 MOTs. Highest fail rate at 9 years old.

How the GLS X166 (GL/GLS) compares

At each age below, see how the GLS X166 (GL/GLS) holds up against other cars the same age. The averages combine all fuel types.

Based on 182,274 tests across 17 Mercedes-Benz models, built around 2018 (7 years old).

Below typicalAbove typicalHigh (28% or more)Highest fail rateMercedes-Benz average
Age / builtFail rateMOT tests
5 yearsbuilt around 2020
16313.5%
6 yearsbuilt around 2019
54611.9%
7 yearsbuilt around 2018
62011.6%
8 yearsbuilt around 2017
61310.0%
9 yearsbuilt around 2016
19815.7%

Fail rate is the share of MOT tests that ended in a fail. Retests count as tests. How we count fail rates Build years are worked out from age, so they are approximate. Tests counted are 2025 MOTs.

What to check before viewing

The model's most common MOT issues, turned into things you can ask about or look for.

Independent inspection

High priority

Have an independent specialist inspect the car before you commit.

Brake discs

High priority

Ask for the date and mileage of the last disc replacement; visually check for a deep wear lip and rust pitting on each disc.

Brake pads

High priority

Ask when the pads were last replaced and check the warning-light history.

Tyres

Worth checking

Check tread depth across the full width on all four; uneven wear suggests alignment or suspension issues.

Vehicle-specific check

Worth checking

Check the car’s number plate on MOT Wise to see its own MOT history and any recalls for its build years.

Other SUVs to compare

Other SUVs, with each one's figures taken at the same age as the GLS X166 (GL/GLS).

  1. 1

    Lexus RX

    Same body type, tested at the same age

    Fail rate
    7.6%
    Fail, no pass in 3 days
    1.3%
    Dangerous
    2.9%
    Still registered at 10 years
    90.4%

    Lower fail rate: 7.6%, against 11.6% for the Mercedes-Benz GLS X166 (GL/GLS), both built around 2018.

    1,815 MOT tests on cars built around 2018

  2. 2

    Lexus NX

    Same body type, tested at the same age

    Fail rate
    9.5%
    Fail, no pass in 3 days
    1%
    Dangerous
    2.7%
    Still registered at 10 years
    88.4%

    Lower fail rate: 9.5%, against 11.6% for the Mercedes-Benz GLS X166 (GL/GLS), both built around 2018.

    4,706 MOT tests on cars built around 2018

  3. 3

    Volkswagen T-Roc

    Same body type, tested at the same age

    Fail rate
    9.6%
    Fail, no pass in 3 days
    0.9%
    Dangerous
    3.9%

    Lower fail rate: 9.6%, against 11.6% for the Mercedes-Benz GLS X166 (GL/GLS), both built around 2018.

    9,233 MOT tests on cars built around 2018

  4. 4

    Porsche Macan

    Same body type, tested at the same age

    Fail rate
    8.7%
    Fail, no pass in 3 days
    2%
    Dangerous
    2.4%
    Still registered at 10 years
    91.6%

    Lower fail rate: 8.7%, against 11.6% for the Mercedes-Benz GLS X166 (GL/GLS), both built around 2018.

    4,936 MOT tests on cars built around 2018

Fail rate
= the share of MOT tests that ended in a fail. Retests count as tests.
Fail, no pass in 3 days
= the share of MOT tests that failed and still hadn't passed 3 days later. A fail that passed a retest within 3 days, even the same day, isn't counted.
Dangerous
= the share of MOT tests where the tester marked a fault as dangerous. It is against the law to drive the car until it is fixed.
Still registered at 10 years
= the share of cars still registered (taxed or declared off the road) 10 years after they were first registered.

How many are still registered

Not enough registration data to show this for the Mercedes-Benz GLS.

The share still registered can reflect demand, the cost of repairs, exports, write-offs and how owners use the car. It isn't proof of how long the car lasts mechanically.

Recall context

46 recalls in all

21 of the 46 GLS X166 (GL/GLS) recalls cover cars built in these years.

  • 1 Critical
  • 20 more

Top concerns

  • Oil foam may develop in the active curve system oil reservoir
  • Installation of A/C drain hoses
  • The bolting of the 48V ground connection under the passenger seat might be fastened with an insufficient torque

For the exact car, check GOV.UK's recall checker with the number plate.

How GLS X166 (GL/GLS) cars have aged

How GLS X166 (GL/GLS) cars have aged

How fail rates have changed as these cars got older. Each line follows cars first registered in about the same year across several years of MOT data. Not a prediction for any one car.

0%10%3456789Age at MOTBuilt around 2019, 3 years old at the time of MOT: 10.2% (324 tests, 2022 data)Built around 2019, 4 years old at the time of MOT: 8.4% (285 tests, 2023 data)Built around 2019, 5 years old at the time of MOT: 10.8% (259 tests, 2024 data)Built around 2019, 6 years old at the time of MOT: 12.8% (235 tests, 2025 data)2019Built around 2018, 3 years old at the time of MOT: 10.1% (582 tests, 2021 data)Built around 2018, 4 years old at the time of MOT: 9.5% (412 tests, 2022 data)Built around 2018, 5 years old at the time of MOT: 12.0% (375 tests, 2023 data)Built around 2018, 6 years old at the time of MOT: 13.5% (348 tests, 2024 data)Built around 2018, 7 years old at the time of MOT: 12.4% (306 tests, 2025 data)2018Built around 2017, 4 years old at the time of MOT: 11.7% (548 tests, 2021 data)Built around 2017, 5 years old at the time of MOT: 12.2% (508 tests, 2022 data)Built around 2017, 6 years old at the time of MOT: 9.5% (441 tests, 2023 data)Built around 2017, 7 years old at the time of MOT: 10.2% (433 tests, 2024 data)Built around 2017, 8 years old at the time of MOT: 10.5% (352 tests, 2025 data)2017Built around 2016, 5 years old at the time of MOT: 11.6% (242 tests, 2021 data)Built around 2016, 6 years old at the time of MOT: 12.2% (238 tests, 2022 data)Built around 2016, 7 years old at the time of MOT: 10.1% (208 tests, 2023 data)Built around 2016, 8 years old at the time of MOT: 11.1% (198 tests, 2024 data)Built around 2016, 9 years old at the time of MOT: 15.7% (198 tests, 2025 data)2016
First registered around 2019First registered around 2018First registered around 2017First registered around 2016
X166 (GL/GLS) variants compared
All generations of this modelNot much data

Most common issues on Mercedes-Benz GLS models of this age

This list covers every Mercedes-Benz GLS built around 2018, whichever generation it is. We don't have a defect list for the X166 (GL/GLS) on its own.

Most common advisories and fails

In order of the share of MOT tests that recorded each one

  1. 1
    Advisory

    Tyre worn close to the legal limit or worn on the edge

    23.2%
    Advisory: 237Fail: 34 (13% of the times it was found)
  2. 2
    Advisory

    Brake pads wearing thin

    6.8%
    Advisory: 52Fail: 5 (9% of the times it was found)
  3. 3
    Advisory

    Brake disc worn, pitted or scored, but not seriously weakened

    6.0%
    Advisory: 60Fail: 0 (0% of the times it was found)
  4. 4
    Minor

    Drive shaft joint cover badly deteriorated

    4.3%
    Advisory: 0Fail: 0 (0% of the times it was found)
  5. 5
    Advisory

    Tyre has a cut that does not reach the ply or cords

    4.2%
    Advisory: 19Fail: 10 (34% of the times it was found)

Based on 620 tests

Looking at a Mercedes-Benz GLS X166 (GL/GLS) right now?

Enter its number plate to see its full MOT history, risk rating and running costs.

Frequently asked questions

Built around 2018 (7 years old), the Mercedes-Benz GLS X166 (GL/GLS) (2013-2019) fails MOTs noticeably less often than typical for this age. This is based on 620 7-year-old MOT tests from DVSA data. Each retest counts as a test.

*The build year is worked out from the date a car was first used on UK roads. For most cars this matches when it was registered, but imports may differ by a few months.

Data sourced from DVSA MOT History API. From 2,140 MOT tests on Mercedes-Benz GLS models first registered between 2013-2019. These figures are a guide, not a guarantee.