Is the Mercedes-Benz SLK reliable?

On MOT evidence the Mercedes-Benz SLK is below average. It passes 69.3% of tests once age and mileage are accounted for, against a national average of 72.3%. That figure covers 61% of the national age and mileage range, which is enough to quote but not to rank. This measures how often the car meets the MOT standard, not how often it breaks down or what a repair costs.

What is the most common MOT failure on a Mercedes-Benz SLK?

The item recorded most often is "A spring or spring component fractured or seriously weakened", which appears in 23.5% of failed Mercedes-Benz SLK tests. Because one failed test can list several items, these shares do not add up to 100%.

What do testers most often warn about on a Mercedes-Benz SLK?

The most common advisory is "Tyre tread depth not in accordance with the requirements", noted on 21.7% of all Mercedes-Benz SLK tests. An advisory is not a failure: it flags something that will likely need attention before the next test.

What mileage does a Mercedes-Benz SLK usually have at its MOT?

The average odometer reading recorded at test is 71,786 miles. This is the mileage across all tested examples of every age, not an annual figure, so treat it as a description of the fleet rather than a target for one car.

Does a Mercedes-Benz SLK get harder to pass as it ages?

Yes. At 9 to 11 years old, 78.7% of Mercedes-Benz SLK tests pass. By fifteen years or more, that falls to 68.5%. Nearly every model follows this pattern, which is why comparing raw pass rates between models is misleading unless age is accounted for.

Are most Mercedes-Benz SLK models petrol or diesel?

Of the Mercedes-Benz SLK cars tested, 76% are petrol, 24% are diesel. Fuel type affects which items tend to fail, particularly emissions and exhaust components.

Model reliability file

Mercedes-Benz SLK MOT pass rate & common failures

From 54,151 recorded MOT tests of the Mercedes-Benz SLK, published by DVSA.

Data updated 29 July 2026

Quick answer

The Mercedes-Benz SLK passes 69.3% of MOT tests once results are adjusted for the age and mileage of the cars tested, against a national average of 72.3%. That is below average. Based on 54,151 tests. Its most commonly recorded failure is spring or spring component fractured or seriously weakened, which appears in 23.5% of failed tests. Cars of this model average 71,786 miles on the odometer when tested.

At a glance

Pass rate, adjusted for age and mileage

69.3%national average72.3%unadjusted71.9%range covered61%

The SLK is 3.0 percentage points below the national pass rate once age and mileage are accounted for, which is below average. The unadjusted figure is 71.9%; the difference is what the age and mileage of this model’s fleet was hiding.

DVSA recorded wording

Most common failure items

Share of failed Mercedes-Benz SLK tests in which each item was recorded. One failed test often lists several items, so these do not sum to 100%.

1.A spring or spring component fractured or seriously weakened23.5%
3,117 occurrencesRoad spring broken or fractured explained
2.A suspension pin, bush or joint excessively worn13.3%
1,762 occurrencesSuspension arm bush worn explained
3.Tyre tread depth not in accordance with the requirements10.9%
1,449 occurrencesTyre worn close to the legal limit explained
4.Brake pipe damaged or excessively corroded9.2%
1,218 occurrencesBrake pipe corroded explained
5.A tyre cords visible or damaged8.3%
1,103 occurrencesTyre ply or cord exposed, or the casing separating explained
6.A tyre seriously damaged6.6%
880 occurrencesTyre damaged or deteriorated explained
7.A suspension pin, bush or joint excessively worn6.2%
819 occurrencesSuspension arm bush worn explained
8.A suspension joint dust cover missing or no longer prevents the ingress of dirt etc5.7%
753 occurrencesSuspension joint dust cover missing or split explained
9.The aim of a headlamp is not within limits laid down in the requirements5.4%
719 occurrencesHeadlamp aim incorrect explained
10.Wiper blade missing or obviously not clearing the windscreen5.0%
666 occurrencesWiper or washer not working properly explained

Warnings without a failure

Most common advisories

Share of all Mercedes-Benz SLK tests carrying each advisory. The denominator differs from the failure list above because an advisory can be issued on a car that passed.

1.Tyre tread depth not in accordance with the requirements21.7%
11,744 testsTyre worn close to the legal limit explained
2.Brake pipe damaged or excessively corroded17.7%
9,591 testsBrake pipe corroded explained
3.A tyre seriously damaged13.4%
7,240 testsTyre damaged or deteriorated explained
4.Brake disc or drum excessively weakened, insecure or fractured12.2%
6,582 testsBrake disc worn, pitted or scored explained
5.A suspension pin, bush or joint excessively worn7.0%
3,771 testsSuspension arm bush worn explained
6.A wheel bearing with excessive play6.6%
3,562 testsWheel bearing has excessive play or is rough explained
7.A brake lining or pad worn below 1.5mm6.1%
3,281 testsBrake drum or shoe worn or contaminated explained
8.A spring or spring component fractured or seriously weakened4.7%
2,527 testsRoad spring broken or fractured explained

How wear changes the picture

Pass rate by vehicle age

9–11 yrs79%

12–14 yrs74%

15+ yrs69%

Bands holding too few tests to be meaningful are omitted rather than shown as a rate.

What gets tested

The SLK fleet

Average mileage recorded at test: 71,786
Fuel mix of tested cars: Petrol75.7%
Diesel24.3%

Trim names grouped into this model (12)

Recorded exactly as DVSA holds them. Trim-level names are rolled up so one model is not split across a dozen thin pages.

SLK 200
SLK 200 KOMPRESSOR
SLK 200K
SLK 230
SLK 250
SLK 250 CDI
SLK 280
SLK 300
SLK 320
SLK 350
SLK 350 AUTO
SLK 55 AMG

Check a specific Mercedes-Benz SLK

A model average tells you the pattern. Its own MOT record tells you the car.

Compare within the range

Other Mercedes-Benz models

Mercedes-Benz A-Class — 73.3% adjusted
Mercedes-Benz C-Class — 77.0% adjusted
Mercedes-Benz E-Class — 78.5% adjusted
Mercedes-Benz GLA — 82.3% adjusted
Mercedes-Benz Vito — 71.0% adjusted
Mercedes-Benz GLC — 85.9% adjusted
All Mercedes-Benz models

Similar test volumes

Compare against other makes

Ford B-Max — 63.8% adjusted, ranked 234
Peugeot Boxer — 71.4% adjusted, ranked 157
Ford Galaxy — 70.3% adjusted, ranked 170
Toyota Avensis — 75.2% adjusted, ranked 107

Common questions

Is the Mercedes-Benz SLK reliable?: On MOT evidence the Mercedes-Benz SLK is below average. It passes 69.3% of tests once age and mileage are accounted for, against a national average of 72.3%. That figure covers 61% of the national age and mileage range, which is enough to quote but not to rank. This measures how often the car meets the MOT standard, not how often it breaks down or what a repair costs.
What is the most common MOT failure on a Mercedes-Benz SLK?: The item recorded most often is "A spring or spring component fractured or seriously weakened", which appears in 23.5% of failed Mercedes-Benz SLK tests. Because one failed test can list several items, these shares do not add up to 100%.
What do testers most often warn about on a Mercedes-Benz SLK?: The most common advisory is "Tyre tread depth not in accordance with the requirements", noted on 21.7% of all Mercedes-Benz SLK tests. An advisory is not a failure: it flags something that will likely need attention before the next test.
What mileage does a Mercedes-Benz SLK usually have at its MOT?: The average odometer reading recorded at test is 71,786 miles. This is the mileage across all tested examples of every age, not an annual figure, so treat it as a description of the fleet rather than a target for one car.
Does a Mercedes-Benz SLK get harder to pass as it ages?: Yes. At 9 to 11 years old, 78.7% of Mercedes-Benz SLK tests pass. By fifteen years or more, that falls to 68.5%. Nearly every model follows this pattern, which is why comparing raw pass rates between models is misleading unless age is accounted for.
Are most Mercedes-Benz SLK models petrol or diesel?: Of the Mercedes-Benz SLK cars tested, 76% are petrol, 24% are diesel. Fuel type affects which items tend to fail, particularly emissions and exhaust components.

How this was worked out

Method and limits

Figures come from the DVSA anonymised MOT testing dataset, published under the Open Government Licence. Only class 4 initial tests are counted: retests are excluded so a car appears once, and abandoned tests are excluded entirely. The adjusted rate is directly standardised across twenty-five age and mileage bands and reweighted onto the national distribution, so this model is compared against cars that have lived a similar life rather than against a younger or lighter-used fleet.

An MOT measures whether a car met a legal standard on the day. It is not a breakdown record, a service history or a running-cost estimate, and a pass rate is a property of a fleet rather than a prediction about one car.