All generations and engines together · 8,967 MOT tests in the 2025 data · typical mileage at age 7: 37k
Computed from DVSA MOT results, all of Great Britain, 2025. Nothing here is opinion.
Share of tests where each item was recorded. The dark tick is the class average across all tracked models; bars are scaled within each group.
The rows that judge the model rather than its keeper. 7,568 tests in this band.
Tyres, pads and stone chips say more about how the car was driven and maintained than about how it was built.
Owner folklore from forums and the motoring press. Most of it never shows up in an MOT, which is why this section exists at all.
The metal folding roof's headlining or seal can come unstuck, most often at the front edge, letting water through onto the passenger's lap in heavy rain. Owners on Mercedes forums describe it worsening over a year even after a specialist re-bonds it, and Mercedes itself has treated leaking as a known issue rather than a one-off. It tends to show from around 5 years old and a re-bond or roof panel replacement runs into four figures.
Separate from the leak, the powered roof can jam partway through opening or closing, or the front catch can refuse to release, usually down to worn microswitches, a weak roof pump or a stretched drive cable rather than anything structural. It is a known nuisance fault across R172-generation folding hardtops (SLK and SLC share the mechanism) and shows at any age once components wear. A specialist diagnosis and repair is normally a few hundred pounds unless a motor or ram needs replacing.
A recurring complaint on the R172 platform is a clonk or knock from the front end over bumps or on lock, usually traced to worn front strut top mounts, anti-roll bar drop links, or (on AMG models) Airmatic strut wear. Forum regulars treat a slight knock as a known, fairly common fault rather than an emergency, but left long enough the links and bushes will fail an MOT. The measured MOT data for this model does show suspension as the standout failure category, which lines up with the forum chatter about clunky front ends, though the data can't say whether it's the strut mounts, drop links or something else in the chain.
The four-cylinder M274 turbo used in the SLC 200/300 can suffer a seized or failed thermostat housing, which stops the engine reaching temperature and can trigger cooling warnings, and worn camshaft actuators that throw fault codes and rough running. Neither is usually terminal but both need attention, with thermostat housing replacement typically a few hundred pounds. This engine is shared across several current Mercedes models so the failure pattern is well documented outside the SLC specifically, not unique to it.
The SLC 250d uses the OM651 diesel four-cylinder found across the wider Mercedes range. A sudden loss of power or limp mode on these engines usually comes down to an EGR cooler internal leak, a blocked DPF, or a failing injector, and owners report all three across the OM651 family. It doesn't appear to be worse in the SLC than in any other OM651-engined Mercedes, but a diesel-specific check is worth doing since it's a rarer engine choice in this model. Repairs range from a few hundred pounds for an EGR clean to over a thousand for injectors or a DPF.
What Car's reliability coverage notes that reported problems on the SLC are generally few, but where they do crop up it's usually electrical gremlins affecting the sat-nav or minor switchgear rather than anything mechanical. These tend to be intermittent and can be fiddly to pin down, sometimes needing a software update or a connector reseated rather than a big repair. Not a big-ticket item on its own, but worth flagging as the most commonly reported niggle.
Built from the two sections above.
Same segment (Coupés, convertibles & GT), best MOT record first. Compare before you shortlist.