Mercedes-Benz C years to avoid — 1.1 million MOT tests ranked

Inspect most carefully: 2020, 2021. Strongest in the data: 2008 or 2010. The ranking uses 1.1 million MOT tests across 21 registration years (2023–2025) and compares each year with all UK cars of the same age. Fuel-type signal: diesels show an average 4.4-point pass-rate deficit on this model. That may reflect mileage and use as well as the car itself, so inspect DPF and emissions history rather than treating fuel type as a verdict.

Every C year, ranked

The age-adjusted MOT index sets 100 as the pass rate of all UK cars registered in the same year and tested in the same calendar year. Higher is better. This prevents an old car being labelled a “bad year” simply because it is old.

Rank	Year	Index	Vs same-age	Pass rate	Tests
1	2008 Strong	104.4	+4.4 pts	69.6%	42,839
2	2010 Strong	104.4	+4.4 pts	71.8%	42,047
3	2014	104.1	+4.1 pts	79.9%	76,814
4	2001	103.9	+3.9 pts	70.4%	3,928
5	2009	103.8	+3.8 pts	70.2%	40,822
6	2002	103.6	+3.6 pts	69.2%	7,620
7	2015	103.5	+3.5 pts	82.3%	103,035
8	2011	103.4	+3.4 pts	72.5%	60,218
9	2007	102.9	+2.9 pts	68.0%	38,374
10	2016	102.5	+2.5 pts	83.9%	110,346
11	2006	101.3	+1.3 pts	65.7%	30,576
12	2017	101.2	+1.2 pts	85.2%	118,299
13	2013	101.2	+1.2 pts	74.6%	72,438
14	2005	101.2	+1.2 pts	65.7%	26,728
15	2012	101.0	+1.0 pts	72.2%	80,699
16	2018	100.8	+0.8 pts	87.1%	84,470
17	2019	100.4	+0.4 pts	88.8%	71,902
18	2004	100.2	+0.2 pts	64.5%	19,932
19	2003	100.2	+0.2 pts	65.2%	13,765
20	2020 Inspect	99.2	-0.8 pts	89.1%	22,240
21	2021 Inspect	99.0	-1.0 pts	89.4%	3,431

Why 2020 and 2021 rank lower

The 2020 cohort passes 89.1% of tests (-0.8 points versus same-age cars) at a median 30,705 miles, with tyres the leading failure system. The 2021 cohort passes 89.4% of tests (-1.0 points versus same-age cars) at a median 28,435 miles, with tyres the leading failure system. This is population-level evidence, not a known-fault list: service history, engine version and the individual MOT record can outweigh the registration-year average.

How to use this before buying

Rankings describe the cohort, not the car. A cherished 2020 example beats a neglected 2008 one — always run the specific reg through the free MOT history check.
Read the advisories. Repeated notes for the same component across years mean the owner has been ignoring it. Decode them in our advisory library.
Fuel matters on this model. The diesel deficit (4.4 points) usually traces to DPF and emissions kit on low-mileage use — check for P2463-type soot codes on the test drive.
Scan before you pay. A 2-minute OBD scan reveals stored faults the dashboard hides — see our scanner guide.

FAQs

Which C years should I avoid?

Based on 1.1 million MOT tests adjusted against cars of the same age, 2020, 2021 are the lower-scoring outliers. That is a prompt for closer inspection, not proof that every car from those years is bad.

What is the best C year to buy used?

2008 and 2010 lead the age-adjusted MOT ranking. The score compares each registration year with all UK cars of the same age; the specific car's history and condition still take priority.

Is the C reliable overall?

Across 1.1 million tests, the median age-adjusted index is 101.3 (100 equals the pass rate of all cars registered in the same year). Use the spread between years as one signal, then check the individual registration.

Methodology: index = 100 + the model-year cohort’s MOT pass-rate difference versus all UK vehicles registered in the same year and tested in the same calendar year. Class 4 initial tests only; retests excluded; at least 1,500 tests per page. “Inspect” years are below both the same-age baseline and the model’s median index by at least 2 points. Association is not proof of a model-year defect. DVSA anonymised data 2023–2025, OGL v3.0.