78.2%
Mercedes-Benz 300
Mercedes-Benz 300 MOT pass rate and common problems
The Mercedes-Benz 300 passed 78.2% of its initial MOT tests in 2025, 5.9 percentage points above the 72.3% UK average. The item testers recorded most often was headlamp aim too low.
Checking a specific car? Its own results, advisories and recorded mileages are in a free MOT history check.
How the 300 compares
Initial MOT tests in 2025, retests excluded. A car that failed and was repaired at the test station counts as a fail.
77.1%
Mercedes-Benz average
72.3%
UK average, all cars
The 300 runs 1.2 points ahead of the Mercedes-Benz average. It is 20th of the 35 Mercedes-Benz models in the data. The average 300 arrived at its test 34.9 years old with 112,339 miles recorded.
A pass rate records whether cars met the roadworthiness standard on test day. It is not a reliability score, and part of any gap reflects how old the tested cars were.
300 MOT pass rate by age
The same 2025 tests split by the car's age at test.
| Age at test | Tests | Pass rate | vs UK average |
|---|---|---|---|
| 3 to 5 years (small sample) | 11 | 90.9% | 18.6 pts above |
| 6 to 10 years (small sample) | 9 | 88.9% | 16.6 pts above |
| 11 years and over | 2,623 | 78.1% | 5.8 pts above |
Too few tests fall into some age groups to compare them reliably. The UK average of 72.3% covers cars of every age, so compare like with like.
Where 300 failures cluster
Every failure item recorded on Mercedes-Benz 300 cars in 2025, grouped into the DVSA's test areas.
Lamps, reflectors and electrical equipment and brakes together account for 48.6% of recorded failure items. These are recorded failures across the model, not faults every car has.
The 10 most common 300 MOT failures
Specific items recorded on Mercedes-Benz 300 cars that failed their 2025 MOT, as a share of all recorded failure items.
Together these 10 items make up 29.4% of everything testers recorded against failed Mercedes-Benz 300 cars. The rest is spread across many smaller items, and one failed test often records several at once.
What to look at on a 300
The recorded failures above, grouped by area, biggest first.
1
Lamps, reflectors and electrical equipment
Recorded most often: headlamp aim too low, position lamp not working, rear fog lamp not working and headlamp aim too high. 12.6% of failure items.
2
Suspension
Recorded most often: ball joint dust cover no longer prevents the ingress of dirt and component mounting prescribed areas prescribed area excessively corroded significantly reducing structural strength. 7.3% of failure items.
3
Visibility
Recorded most often: wipers does not clear the windscreen effectively and washers provides insufficient washer liquid. 5% of failure items.
4
Noise, emissions and leaks
Recorded most often: non catalyst emissions emissions carbon monoxide content excessive. 2.3% of failure items.
The car's own MOT history matters more than any model average. A free MOT history check shows whether a specific 300 has failed on these items before, or had them noted as advisories. Buying one? See the used Mercedes-Benz 300 buying guide.
Already found one?
Check its finance, write-off, theft, mileage and keeper history with a £15 vehicle history report.
Mercedes-Benz 300 MOT FAQs
What is the Mercedes-Benz 300 MOT pass rate?
78.2% of Mercedes-Benz 300 cars passed their initial MOT first time in 2025, from 2,645 tests. That is 5.9 percentage points above the 72.3% average for all cars, and ranks 224th of 575 models.
What does a Mercedes-Benz 300 most commonly fail its MOT on?
The item testers recorded most often on Mercedes-Benz 300 cars failing their 2025 MOT was headlamp aim too low, on 4.5% of failure items. Next were ball joint dust cover no longer prevents the ingress of dirt (3.7%) and component mounting prescribed areas prescribed area excessively corroded significantly reducing structural strength (3.6%).
Which area causes the most Mercedes-Benz 300 MOT failures?
Across every recorded failure item, the largest area was lamps, reflectors and electrical equipment at 29.7%, followed by brakes at 18.9%.
Does this mean every Mercedes-Benz 300 has these problems?
No. These are the items testers recorded across every Mercedes-Benz 300 that failed in 2025. They show where the model most often needs attention, not the condition of any individual car.
How do I see a specific Mercedes-Benz 300's MOT history?
Enter its registration on the free Carpeep MOT history check to see that car's own test results, failures, advisories and recorded mileages.
MOT figures are aggregated from the DVSA MOT Anonymised data set for 2025: class 4 initial tests, retests excluded, with failure items from failed tests (advisories and minor defects excluded), licensed under the Open Government Licence v3.0. MOT results describe roadworthiness at test, not mechanical reliability.