Verdict
The Mercedes-Benz 300 passes its MOT first time on 75.7% of tests, 8.6 points higher than a typical car of the same age and mileage (67.1%). That puts it ahead of 87% of cars on UK roads once age and mileage are taken into account.
By year of first registration, the 1989 300 does best (beats 91% of cars) and the 1990 worst (beats 82%).
Better than average on lights & electrics, brakes, suspension.
Watch these weak spots
Best and worst years
By year of first registration, ranked against all cars on UK roads after adjusting for age and mileage. Green = better than half of cars.
Engines
All years, most common first. Grades compare each car with cars of the same age and mileage (A = best 20% of cars on UK roads, E = worst 20%), so an older or higher-mileage car can grade above one with a higher pass rate.
| Engine | Pass rate | Rank | Grade |
|---|---|---|---|
| 3.0 Petrol | 76.2% | Beats 88% | A |
| 3.0 Diesel | 65.2% | Beats 65% | B |
Where it fails
Each area compared with a typical car of the same age and mileage, in points of pass rate. Tap or hover an area to see what to check.
Every MOT area
Share of tests failing on each area, against a typical car of the same age and mileage (black line).
Buying one or MOT due? Check these
- Headlight aim
Park facing a wall at night: both dipped beams should sit level and dip to the left. - Windscreen washers
Test the washers and wipers: a cheap fix, but a very common MOT fail. - Sidelights
Walk around with the lights on: bulb failures are the easiest MOT fails to avoid. - Brake performance
On the test drive, brake firmly: the car should stop straight with no pulsing through the pedal. - Exhaust system
Listen for a blowing exhaust at start-up and look for heavy corrosion underneath. - Tyre damage & cracking
Look for cuts, bulges and cracking on both sidewalls of every tyre.
Pass rate by mileage
First-time pass rate by mileage at the test.
Most common MOT failures
| Item | This car | Typical | vs typical |
|---|---|---|---|
| Headlight aim | 3.4% | 4.6% | 0.7× |
| Windscreen washers | 2.6% | 3.9% | 0.7× |
| Sidelights | 2.3% | 3.6% | 0.6× |
| Windscreen wipers | 2.1% | 3.0% | 0.7× |
| Non catalyst emissions | 1.9% | 2.4% | 0.8× |
| Rear fog light | 1.8% | 3.2% | 0.6× |
| Component mounting prescribed areas | 1.6% | 3.9% | 0.4× |
| Brake performance | 1.6% | 2.6% | 0.6× |
| Exhaust system | 1.5% | 2.6% | 0.6× |
| Tyre damage & cracking | 1.5% | 1.7% | 0.9× |
Specific defects found
Tester wording for the most frequent failure items, per 1,000 tests.
| Defect | per 1,000 |
|---|---|
| The aim of a headlamp is not within limits laid down in the requirements | 33.9 |
| Windscreen washers not working or not providing sufficient fluid to clear the windscreen | 25.5 |
| Emissions levels exceed default limits | 22.7 |
| A direction indicator lamp missing, inoperative or in the case of a multiple light source more than 1/2 not functioning | 18.6 |
| An obligatory rear fog lamp missing, or a front or rear fog lamp inoperative or in the case of a multiple light source more than 1/2 not functioning | 17.9 |
| The strength or continuity of the load bearing structure within 30cm of any sub-frame, spring or suspension component mounting (a 'prescribed area') is significantly reduced or inadequately repaired | 17.9 |
| Wiper blade missing or obviously not clearing the windscreen | 17.1 |
| A suspension joint dust cover missing or no longer prevents the ingress of dirt etc | 16.6 |
Pick a make and model to see its MOT pass rate, best and worst years and weak spots.
Every year and engine
Tap a year to see its engines. Grades compare each car with cars of the same age and mileage (A = best 20% of cars on UK roads, E = worst 20%), so an older or higher-mileage car can grade above one with a higher pass rate.
1993 Mercedes-Benz 3001 engine74.5% passA
| Engine | Pass rate | Rank | Grade |
|---|---|---|---|
| 3.0 Petrol | 74.5% | Beats 90% | A |
1992 Mercedes-Benz 3002 engines73.6% passA
| Engine | Pass rate | Rank | Grade |
|---|---|---|---|
| 3.0 Petrol | 76.2% | Beats 93% | A |
| 3.0 Diesel | 65.2% | Beats 65% | B |
1991 Mercedes-Benz 3001 engine73.6% passA
| Engine | Pass rate | Rank | Grade |
|---|---|---|---|
| 3.0 Petrol | 73.6% | Beats 83% | A |
1990 Mercedes-Benz 3001 engine74.1% passA
| Engine | Pass rate | Rank | Grade |
|---|---|---|---|
| 3.0 Petrol | 74.1% | Beats 82% | A |
1989 Mercedes-Benz 3001 engine78.2% passA
| Engine | Pass rate | Rank | Grade |
|---|---|---|---|
| 3.0 Petrol | 78.2% | Beats 91% | A |
1988 Mercedes-Benz 3001 engine76.7% passA
| Engine | Pass rate | Rank | Grade |
|---|---|---|---|
| 3.0 Petrol | 76.7% | Beats 86% | A |
1987 Mercedes-Benz 3001 engine78.2% passA
| Engine | Pass rate | Rank | Grade |
|---|---|---|---|
| 3.0 Petrol | 78.2% | Beats 91% | A |
1986 Mercedes-Benz 3001 engine76.4% passA
| Engine | Pass rate | Rank | Grade |
|---|---|---|---|
| 3.0 Petrol | 76.4% | Beats 84% | A |
FAQ
What is the Mercedes-Benz 300 MOT pass rate?
75.7% of MOT tests on the Mercedes-Benz 300 were passed first time, based on 25,458 tests between 2018 and 2026 of cars first registered 1986–1993. A typical car of the same age and mileage passes 67.1% of the time.
Is the Mercedes-Benz 300 reliable?
On MOT results it rates A (excellent): it passes first time more often than a typical car of the same age and mileage and does better than 87% of cars on UK roads. MOT results cover safety and emissions items, not every kind of breakdown.
Which Mercedes-Benz 300 year is best?
Among years with enough data, the 1989 300 does best for its age and mileage: it beats 91% of cars on UK roads. The 1990 does worst: it beats 82%.
What are the most common MOT failures on the Mercedes-Benz 300?
The most common failure items are headlight aim, windscreen washers, sidelights. Compared with similar cars, ball joint dust covers comes up 2.0× as often.