78.2%
Mercedes-Benz 300 pass rate
Used Mercedes-Benz 300 buying guide
In 2025, Mercedes-Benz 300 cars passed 78.2% of 2,645 initial MOT tests, 5.9 points above the 72.3% UK average. Here is where it fails and what to check before you buy.
Looking at a specific 300? Check its finance, write-off, stolen, mileage and keeper history. £15, no account needed.
Mercedes-Benz 300 MOT record in brief
Initial MOT tests in 2025, retests excluded.
72.3%
UK average, all cars
+5.9
percentage points above average
Ranked on pass rate the 300 sits 224th of 575 models in the data. Mercedes-Benz as a brand averaged 77.1%, so this model runs 1.2 points ahead of its own brand.
A pass rate is not a reliability score. The full Mercedes-Benz 300 MOT record has the pass rate by age, every common failure and how the 300 compares with similar cars.
300 fuel types
Petrol was the most common fuel among Mercedes-Benz 300 cars tested in 2025. Diesel still made up 16.9% of tests.
Where the 300 fails its MOT
Where Mercedes-Benz 300 cars that failed their 2025 MOT were marked down, as a share of all recorded failure items.
The specific items testers recorded most often were headlamp aim too low (4.5%), 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%). See every common 300 MOT failure.
These are DVSA failure records across every Mercedes-Benz 300 that failed, not a claim that every 300 has these problems.
What should you check when buying a used 300?
The areas above, most common first, and what an MOT tester looks at in each.
1
Lamps, reflectors and electrical equipment
Walk round with every light on: headlights, brake lights, indicators, fog lights and the number plate lamp. Check no warning lights stay on after starting. 29.7% of 300 failure items.
2
Brakes
Make sure the pedal feels firm, the car stops in a straight line, the handbrake holds on a slope and no brake warning light is showing. 18.9% of 300 failure items.
3
Suspension
Listen for knocks over bumps, check the car sits level, and look for leaking shock absorbers and split rubber gaiters. 15.3% of 300 failure items.
4
Body, chassis, structure
Look underneath and along the sills for corrosion, and check for damaged or poorly repaired panels. 10.7% of 300 failure items.
5
Visibility
Check the windscreen for chips or cracks in the driver's view, and that the wipers and washers clear it properly. 7.9% of 300 failure items.
None of this replaces the car's own record. Run a free MOT history check on the registration to see every test, advisory and recorded mileage for that car.
What the MOT record doesn't tell you
Knowing Mercedes-Benz 300 failures cluster around lamps, reflectors and electrical equipment and brakes tells you what to inspect. It tells you nothing about whether the car is safe to buy. An MOT does not show money still owed on the car, a write-off, a theft record or a clocked odometer.
Check the exact 300 you are looking at. One £15 report, instant results, backed by a £30,000 data guarantee. More on the Mercedes-Benz history check.
- Outstanding finance
- Write-off records
- Stolen markers
- Mileage history
- Previous keepers
Other used Mercedes-Benz models
The most-tested Mercedes-Benz models in 2025, with how their MOT pass rate compares with the 300.
- Used Mercedes-Benz A-Class 78.4% MOT pass rate
- Used Mercedes-Benz C-Class 74.7% MOT pass rate
- Used Mercedes-Benz E-Class 77.4% MOT pass rate
- Used Mercedes-Benz GLA 83.3% MOT pass rate
- Used Mercedes-Benz Vito 67.3% MOT pass rate
- Used Mercedes-Benz GLC 86.4% MOT pass rate
See all 35 Mercedes-Benz models ranked by MOT pass rate.
Used Mercedes-Benz 300 FAQs
Is the Mercedes-Benz 300 reliable?
MOT data does not measure reliability. It records whether a car met the roadworthiness standard on the day of its test. What it does show is a 78.2% first-time pass rate for the Mercedes-Benz 300 across 2,645 tests in 2025, above the 72.3% average for all cars.
What should I check before buying a used Mercedes-Benz 300?
On the car itself, start with the areas it most often fails on: lamps, reflectors and electrical equipment, brakes and suspension. Then check the individual car's history: outstanding finance, insurance write-off records, stolen markers, mileage and previous keepers. None of these appear in the MOT record or on the V5C.
How do I check a Mercedes-Benz 300's history?
Enter the registration of the specific car. A Carpeep car history check reports outstanding finance, write-off category, stolen markers, mileage history, previous keepers, MOT and tax status, import and export markers and scrapped status in one £15 report.
MOT figures are aggregated from the DVSA MOT Anonymised data set for 2025 (class 4 initial tests, retests excluded), licensed under the Open Government Licence v3.0. MOT results describe roadworthiness at test, not mechanical reliability.