Mercedes 300 MOT Pass Rate
Overall pass rate across all manufacture years, based on 47,510 real MOT test results. Failure rate: 32.2%.
Data from official DVSA MOT testing records
Mercedes 300 MOT Reliability Overview
The Mercedes 300 is a relatively common sight on UK roads, with 47,510 MOT test results recorded in our database spanning 35 manufacture years. It has an overall MOT pass rate of 67.8% and a failure rate of 32.2%, which is slightly above the UK average of approximately 37%.
Based on this data, the Mercedes 300 earns a "Good" reliability rating. The average Mercedes 300 presents for MOT with approximately 110,596 miles on the clock. Manufacture year matters: 2007 models achieve the highest pass rate at 88.6%, while 1981 models have the lowest at 44.8%. This 43.8 percentage point difference suggests notable variation in build quality or component durability across production years.
The most common MOT failure for the Mercedes 300 is Brakes, affecting 24.4% of all tests. Brake-related failures include worn brake pads, corroded brake discs, leaking brake lines, and faulty brake servos. These are safety-critical components — any brake deficiency will result in an MOT fail. The second most common issue is Suspension at 21.4%. Lamps, Reflectors and Electrical Equipment rounds out the top three at 20.3%. Together, these top 3 failure categories account for a significant portion of all MOT failures for this model.
Top failures across all manufacture years combined. Individual year pages may show different top failures.
What Fails Most
Best Year to Buy
📈 How Each Vintage Ages
Tracking how each manufacture year's MOT pass rate changes as the car ages. Showing 8 vintages — click year chips to highlight.
Multi-line chart showing how different Mercedes 300 vintages degrade over time, from age 3 to 31 years.
Only vintages with 100+ tests in at least 3 different test years are shown. Fleet average is the UK-wide pass rate for all cars at each age.
📉 How Age Affects Reliability
MOT failure rate by vehicle age for the Mercedes 300. The dashed red line marks when the manufacturer warranty typically expires (3 years).
Line chart showing MOT failure rate by vehicle age from 11 to 20 years, with warranty expiry marked at 3 years.
💡 What does the warranty cliff mean?
The Mercedes 300 shows a relatively stable failure rate after warranty — the change of 0% is negligible. Peak failure occurs at age 15 (47.4% fail rate).
Note: pass rates may improve for very old vehicles due to survivorship bias — only well-maintained cars remain on the road.
Pass Rate by Manufacture Year
* High Fail Rate badge indicates an MOT pass rate below 65% (failure rate above 35%).
What Fails on This Car?
Click a category to see specific failure items.
View as table
| Rank | Failure Category | Rate (%) | Count |
|---|---|---|---|
| 1 | Brakes | 36.5% | 17,363 |
| 2 | Suspension | 30.6% | 14,519 |
| 3 | Lamps, Reflectors And Electrical Equipment | 27.9% | 13,279 |
| 4 | Tyres | 13.8% | 6,566 |
| 5 | Exhaust, Fuel And Emissions | 11.8% | 5,590 |
| 6 | Driver's View Of The Road | 9.6% | 4,555 |
| 7 | Steering | 7.9% | 3,766 |
| 8 | Body, Structure And General Items | 5.4% | 2,553 |
| 9 | Registration Plates And Vin | 2.5% | 1,189 |
| 10 | Seat Belts And Supplementary Restraint Systems | 2.3% | 1,076 |
| 11 | Body, Chassis, Structure | 0.7% | 318 |
| 12 | Road Wheels | 0.6% | 288 |
| 13 | Non-component Advisories | 0.5% | 233 |
| 14 | Items Not Tested | 0.5% | 231 |
Failures per 10,000 Miles
avg. 110,596 miFor every 10,000 miles driven, this shows what percentage of MOT tests fail for each category. This accounts for how far cars are actually driven, not just raw pass/fail counts.
View as table
| Category | Rate / 10K mi | Raw % | Count |
|---|---|---|---|
| Brakes | 3.30 | 36.5% | 17,363 |
| Suspension | 2.76 | 30.6% | 14,519 |
| Lamps & Electrical | 2.53 | 27.9% | 13,279 |
| Tyres | 1.25 | 13.8% | 6,566 |
| Emissions & Exhaust | 1.06 | 11.8% | 5,590 |
| Visibility | 0.87 | 9.6% | 4,555 |
| Steering | 0.72 | 7.9% | 3,766 |
| Body & Structure | 0.55 | 6.1% | 2,871 |
| Registration Plates and VIN | 0.23 | 2.5% | 1,189 |
| Seat Belts | 0.20 | 2.3% | 1,076 |
| Wheels | 0.05 | 0.6% | 288 |
| Non-component advisories | 0.04 | 0.5% | 233 |
| Items Not Tested | 0.04 | 0.5% | 231 |
🚗 Similar Cars to Consider
Mileage at MOT
The average Mercedes 300 has 110,596 miles when tested for MOT.
📊 Mileage-Adjusted Failure Rate
How often this car fails MOT relative to how much it's driven — a fairer comparison than raw pass rate.
The Mercedes 300 has a mileage-adjusted failure rate of 2.91% per 10,000 miles driven. The average across all makes is 5.38%, so this model is better than average.
About Mercedes 300 MOT Data
The Mercedes 300 is a relatively common sight on UK roads, with 47,510 MOT test results recorded in our database spanning 35 manufacture years. It has an overall MOT pass rate of 67.8% and a failure rate of 32.2%, which is slightly above the UK average of approximately 37%.
For Mercedes 300 owners, these results suggest a reliable vehicle that generally passes its MOT without major issues. Focus your pre-MOT checks on brakes and suspension for the best chance of a first-time pass. Use our detailed year-by-year breakdown and failure analysis below to understand how your specific 300 is likely to perform.
Brakes — 24.4% of failures
Brakes issues account for 24.4% of MOT failures on the Mercedes 300. Brake-related failures include worn brake pads, corroded brake discs, leaking brake lines, and faulty brake servos. These are safety-critical components — any brake deficiency will result in an MOT fail. Typical repair costs: £150–400. Pre-MOT check: Listen for squealing or grinding noises. Check brake pedal feel — if it feels spongy or goes to the floor, have the system inspected immediately. Look at brake pad thickness through the wheel spokes (minimum 3mm).
Suspension — 21.4% of failures
Suspension issues account for 21.4% of MOT failures on the Mercedes 300. Suspension failures typically involve worn bushes, leaking shock absorbers, broken coil springs, and damaged suspension arms. These affect ride quality, tyre wear, and road holding. Typical repair costs: £200–500. Pre-MOT check: Look for uneven tyre wear, listen for clunking over bumps, and check if the car pulls to one side. A bouncy ride suggests worn shock absorbers. Visually inspect coil springs for cracks.
Lamps, Reflectors and Electrical Equipment — 20.3% of failures
Lamps, Reflectors and Electrical Equipment issues account for 20.3% of MOT failures on the Mercedes 300. Lighting failures cover all external lights: headlights, tail lights, brake lights, indicators, fog lights, and reflectors. A single blown bulb will cause an MOT fail. This is one of the most preventable failure categories. Typical repair costs: £5–50. Pre-MOT check: Walk around the car and check every light — headlights (dipped and main beam), side lights, tail lights, brake lights, indicators, hazard lights, reverse light, rear fog light, and number plate lights. Replace any blown bulbs before the test.
Frequently Asked Questions
What is the MOT pass rate for the Mercedes 300?
Based on 47,510 MOT tests in our database, the Mercedes 300 has an overall pass rate of 67.8% (32.2% fail rate).
What are the most common MOT failures on a Mercedes 300?
The top 3 reasons a Mercedes 300 fails its MOT are: 1. Brakes (24.4%), 2. Suspension (21.4%), 3. Lamps, Reflectors and Electrical Equipment (20.3%). Check these areas before booking your MOT.
Is the Mercedes 300 reliable?
With a 32.2% MOT failure rate, the 300 is more reliable than average compared to the UK average of ~40%.
What should I check before an MOT on my Mercedes 300?
Based on failure data, focus on: Brakes (24.4%); Suspension (21.4%); Lamps, Reflectors and Electrical Equipment (20.3%). These are the areas most likely to cause a fail. Also check all lights, tyres (minimum 1.6mm tread), and windscreen condition — these are quick wins that apply to all cars.
Based on DVSA anonymised MOT test data (2005–2024). Crown copyright, Open Government Licence v3.0.