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Mercedes-Benz SLK R171 (2nd gen) (2004-2010) reliability

At a glance

Mercedes-Benz SLK R171 (2nd gen) built around 2010: about average at the MOT

Mercedes-Benz SLK R171 (2nd gen) models built around 2010 fail their MOT about as often as similar cars the same age. An independent inspection matters more than the wider numbers on cars this old.

Looking at a Mercedes-Benz SLK R171 (2nd gen) right now?

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

Key figure

24% of MOT tests on Mercedes-Benz SLK R171 (2nd gen) models built around 2010 ended in a fail (retests included), against 22% for similar cars the same age.

Most common issue

The most common MOT issue on Mercedes-Benz SLK R171 (2nd gen) models built around 2010 involves the brakes.

Mercedes-Benz SLK R171 (2nd gen)
excellent reliability2004-2010ConvertiblePETROL

Based on 27,512 tests of SLK models registered 2004-2010.

About 1 in 12 SLK R171 (2nd gen) MOTs (8.3%) failed and still hadn't passed 3 days later. That's for cars built around 2010 (15 years old), all fuels combined.

Based on 2,892 tests (DVSA MOT results, 2025). 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 SLK R171 (2nd gen) MOTs (6.3%) found at least one dangerous defect. These are cars built around 2010 (15 years old).

Based on 2,892 tests (DVSA MOT results, 2025). Dangerous is the most serious grade an MOT gives: a direct risk to road safety.

R171 (2nd gen) fail rate by age

Below typicalAbove typicalHigh (28% or more)Highest fail rateUK average for cars this age
Age / builtFail rateMOT tests
14 yearsbuilt around 2011
1,17023.5%
15 yearsbuilt around 2010
2,89224.2%
16 yearsbuilt around 2009
3,34924.8%
17 yearsbuilt around 2008
4,29125.1%
18 yearsbuilt around 2007
4,26625.5%
19 yearsbuilt around 2006
4,83125.3%
20 yearsbuilt around 2005
5,30426.4%
21 yearsbuilt around 2004
1,40925.6%

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 20 years old.

How the SLK R171 (2nd gen) compares

At each age below, see how the SLK R171 (2nd gen) holds up against other cars the same age. The averages combine all fuel types.

Based on 57,644 tests across 15 Mercedes-Benz models, built around 2010 (15 years old).

Below typicalAbove typicalHigh (28% or more)Highest fail rateMercedes-Benz average
Age / builtFail rateMOT tests
14 yearsbuilt around 2011
1,17023.5%
15 yearsbuilt around 2010
2,89224.2%
16 yearsbuilt around 2009
3,34924.8%
17 yearsbuilt around 2008
4,29125.1%
18 yearsbuilt around 2007
4,26625.5%
19 yearsbuilt around 2006
4,83125.3%
20 yearsbuilt around 2005
5,30426.4%
21 yearsbuilt around 2004
1,40925.6%

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.

Brake pipes and hoses

High priority

Look under the car for corrosion or chafing on the rigid brake pipes near the rear axle.

Suspension bushes and joints

Worth checking

Listen for knocks over speed bumps and ask about recent control-arm or anti-roll-bar work.

Tyres

Worth checking

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

Suspension springs

Worth checking

Check ride height is even side-to-side and look for cracked or rusted coils.

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 convertibles to compare

Other convertibles, with each one's figures taken at the same age as the SLK R171 (2nd gen).

  1. 1

    BMW Z4

    Same body type, tested at the same age

    Fail rate
    16.6%
    Fail, no pass in 3 days
    4.9%
    Dangerous
    5.3%
    Still registered at 10 years
    96%

    Lower fail rate: 16.6%, against 24.2% for the Mercedes-Benz SLK R171 (2nd gen), both built around 2010.

    2,800 MOT tests on cars built around 2010

  2. 2

    Mazda MX-5

    Same body type, tested at the same age

    Fail rate
    22.1%
    Fail, no pass in 3 days
    6.8%
    Dangerous
    3.8%
    Still registered at 10 years
    97.6%

    Lower fail rate: 22.1%, against 24.2% for the Mercedes-Benz SLK R171 (2nd gen), both built around 2010.

    2 critical recall campaigns matching this model/build period.

    5,754 MOT tests on cars built around 2010

  3. 3

    Volvo C70

    Same body type, tested at the same age

    Fail rate
    30.9%
    Fail, no pass in 3 days
    10%
    Dangerous
    8.9%

    No clear edge over the Mercedes-Benz SLK R171 (2nd gen) on these figures.

    1,063 MOT tests on cars built around 2010

  4. 4

    Volkswagen Eos

    Same body type, tested at the same age

    Fail rate
    28%
    Fail, no pass in 3 days
    8.3%
    Dangerous
    8.2%
    Still registered at 10 years
    65.1%

    No clear edge over the Mercedes-Benz SLK R171 (2nd gen) on these figures.

    2 critical recall campaigns matching this model/build period.

    1,965 MOT tests on cars built around 2010

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

93%of all Mercedes-Benz SLK cars first registered in 2014 to 2015 were still registered 10 years later. This is the whole model, not only this generation.

UK average for cars first registered in 2014 to 2015: 92% · About typical

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.

Source: DfT vehicle licensing statistics (VEH0124).

Recall context

26 recalls in all

3 of the 26 SLK R171 (2nd gen) recalls cover cars built in these years.

  • 3 recalls

Top concerns

  • The driver's air bag may have a chemical change to its propellant over time
  • Faulty control unit may cause vehicle to perform outside specification
  • Engine emergency shut off on board diagnosis or tank/speedo signal may be affected

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

What has gone wrong on SLK R171 (2nd gen) cars built around 2010

The share of petrol cars that have ever failed an MOT on each part of the car. Based on 383 cars.

Structural systems

Suspension
62%
Emissions
22%
Bodywork
20%
Steering
2%

Wear items

Tyres
52%
Lighting
40%
Brakes
39%

Rust, which the MOT calls corrosion: 20% of these cars show rust-related issues at this age.

Check the sills, subframe and brake pipes before you decide.

How SLK R171 (2nd gen) cars have aged

How SLK R171 (2nd gen) 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%20%111315171921Age at MOTBuilt around 2010, 11 years old at the time of MOT: 21.3% (1,556 tests, 2021 data)Built around 2010, 12 years old at the time of MOT: 21.1% (1,487 tests, 2022 data)Built around 2010, 13 years old at the time of MOT: 21.7% (1,453 tests, 2023 data)Built around 2010, 14 years old at the time of MOT: 23.6% (1,468 tests, 2024 data)Built around 2010, 15 years old at the time of MOT: 23.3% (1,388 tests, 2025 data)2010Built around 2009, 12 years old at the time of MOT: 22.5% (1,815 tests, 2021 data)Built around 2009, 13 years old at the time of MOT: 22.4% (1,752 tests, 2022 data)Built around 2009, 14 years old at the time of MOT: 24.1% (1,736 tests, 2023 data)Built around 2009, 15 years old at the time of MOT: 23.2% (1,642 tests, 2024 data)Built around 2009, 16 years old at the time of MOT: 23.5% (1,611 tests, 2025 data)2009Built around 2008, 13 years old at the time of MOT: 23.9% (2,533 tests, 2021 data)Built around 2008, 14 years old at the time of MOT: 23.1% (2,444 tests, 2022 data)Built around 2008, 15 years old at the time of MOT: 24.7% (2,457 tests, 2023 data)Built around 2008, 16 years old at the time of MOT: 24.0% (2,331 tests, 2024 data)Built around 2008, 17 years old at the time of MOT: 24.3% (2,247 tests, 2025 data)2008Built around 2007, 14 years old at the time of MOT: 23.6% (2,707 tests, 2021 data)Built around 2007, 15 years old at the time of MOT: 24.0% (2,575 tests, 2022 data)Built around 2007, 16 years old at the time of MOT: 25.3% (2,500 tests, 2023 data)Built around 2007, 17 years old at the time of MOT: 25.8% (2,403 tests, 2024 data)Built around 2007, 18 years old at the time of MOT: 24.9% (2,296 tests, 2025 data)2007Built around 2006, 15 years old at the time of MOT: 24.2% (2,879 tests, 2021 data)Built around 2006, 16 years old at the time of MOT: 25.6% (2,824 tests, 2022 data)Built around 2006, 17 years old at the time of MOT: 25.6% (2,690 tests, 2023 data)Built around 2006, 18 years old at the time of MOT: 25.9% (2,585 tests, 2024 data)Built around 2006, 19 years old at the time of MOT: 25.7% (2,449 tests, 2025 data)2006Built around 2005, 16 years old at the time of MOT: 26.0% (4,096 tests, 2021 data)Built around 2005, 17 years old at the time of MOT: 24.3% (3,769 tests, 2022 data)Built around 2005, 18 years old at the time of MOT: 26.8% (3,757 tests, 2023 data)Built around 2005, 19 years old at the time of MOT: 25.3% (3,451 tests, 2024 data)Built around 2005, 20 years old at the time of MOT: 26.0% (3,175 tests, 2025 data)2005Built around 2004, 17 years old at the time of MOT: 26.7% (2,080 tests, 2021 data)Built around 2004, 18 years old at the time of MOT: 26.4% (1,881 tests, 2022 data)Built around 2004, 19 years old at the time of MOT: 26.4% (1,738 tests, 2023 data)Built around 2004, 20 years old at the time of MOT: 25.8% (1,598 tests, 2024 data)Built around 2004, 21 years old at the time of MOT: 25.6% (1,409 tests, 2025 data)2004
First registered around 2010First registered around 2009First registered around 2008First registered around 2007
How each part holds up as R171 (2nd gen) cars age

How each part holds up as R171 (2nd gen) cars age

The share of petrol cars built 2005-2008 that have ever failed an MOT on each part of the car. Rates usually rise with age, but can dip slightly as cars leave the road.

Part of the car17 years18 years19 years20 years
Suspension66%76%62%69%
Brakes44%45%39%39%
Emissions13%20%22%28%
Tyres49%50%52%55%
Lighting32%38%40%46%
Bodywork7%9%20%21%
Steering1%1%2%2%
Corrosion14%19%20%23%

Based on petrol cars in the 2005-2008 build-year band, from 273 to 497 cars at each age.

R171 (2nd gen) variants compared
All generations of this modelEnough data

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

This list covers every Mercedes-Benz SLK built around 2010, whichever generation it is. We don't have a defect list for the R171 (2nd gen) on its own.

Most common advisories and fails

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

  1. 1
    Advisory

    Suspension arm pin or bush worn, but not moving too much

    16.1%
    Advisory: 556Fail: 188 (25% of the times it was found)
  2. 2
    Advisory

    Brake pipe corroded or covered in grease

    15.8%
    Advisory: 695Fail: 85 (11% of the times it was found)
  3. 3
    Advisory

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

    15.5%
    Advisory: 620Fail: 48 (7% of the times it was found)
  4. 4
    Advisory

    Tyre slightly damaged, cracking or perishing

    13.0%
    Advisory: 471Fail: 100 (18% of the times it was found)
  5. 5
    Advisory

    Coil spring corroded

    8.1%
    Advisory: 136Fail: 174 (56% of the times it was found)

Based on 2,892 tests

Looking at a Mercedes-Benz SLK R171 (2nd gen) right now?

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

Frequently asked questions

Built around 2010 (15 years old), the Mercedes-Benz SLK R171 (2nd gen) (2004-2010) fails MOTs noticeably less often than typical for this age. This is based on 2,892 15-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 27,512 MOT tests on Mercedes-Benz SLK models first registered between 2004-2010. These figures are a guide, not a guarantee.