💨 Noise, emissions and leaks MOT Failures
This covers exhaust emissions testing, excessive noise from the exhaust system, oil or fuel leaks, and catalyst efficiency. Diesel and petrol cars have different emission limits.
Data from official DVSA MOT testing records
✅ Best 20 — Lowest Noise, emissions and leaks Failure Rate
These models have the lowest noise, emissions and leaks failure rate in MOT testing. Great choices if you want to avoid noise, emissions and leaks problems.
| # | Make | Model | Failure Rate | Total Tests |
|---|---|---|---|---|
| 1 | Honda | Jazz I-vtec Ex Cvt | 0% | 8,545 |
| 2 | Smart (mcc) | Fortwo | 0% | 126,973 |
| 3 | Toyota | Yaris Icon Hev Cvt | 0% | 12,084 |
| 4 | Lexus | Ux | 0% | 26,867 |
| 5 | Lexus | Is250c | 0% | 6,210 |
| 6 | Bentley | Continental Gtc | 0% | 9,963 |
| 7 | Mercedes-Benz | Slk | 0% | 355,459 |
| 8 | Nissan | Pulsar | 0% | 121,250 |
| 9 | Mitsubishi | Eclipse | 0% | 35,324 |
| 10 | Mercedes-Benz | C350 Blue-cy Sport Cdi A | 0% | 5,369 |
| 11 | Mercedes-Benz | C | 0% | 2,408,350 |
| 12 | Mercedes-Benz | A160 Classic Se Cvt | 0% | 5,752 |
| 13 | MG | 5 | 0% | 6,855 |
| 14 | Tesla | Model 3 Long Range Awd | 0% | 66,623 |
| 15 | Hyundai | I10 Se Connect Mpi | 0% | 8,722 |
| 16 | Toyota | Yaris Design Hev Cvt | 0% | 22,110 |
| 17 | Mercedes-Benz | 190 E | 0% | 11,502 |
| 18 | Skoda | Octavia Se Tdi Cr | 0% | 5,535 |
| 19 | Toyota | Yaris Tr Vvt-i | 0% | 14,459 |
| 20 | BMW | 116d Efficientdynamics | 0% | 10,357 |
❌ Worst 20 — Highest Noise, emissions and leaks Failure Rate
These models have the highest noise, emissions and leaks failure rate. Consider extra inspection before buying.
| # | Make | Model | Failure Rate | Total Tests |
|---|---|---|---|---|
| 1 | Alfa Romeo | 146 | 44.5% | 8,365 |
| 2 | Kia | Pride | 41.9% | 16,102 |
| 3 | Alfa Romeo | 145 | 41.1% | 8,367 |
| 4 | Citroen | Saxo | 38.3% | 927,263 |
| 5 | Mitsubishi | Ralliart Fto | 36.9% | 5,963 |
| 6 | Ford | Escort Lx | 35.3% | 7,253 |
| 7 | Peugeot | 106 | 34% | 1,019,077 |
| 8 | Rover | 414 | 33.9% | 85,984 |
| 9 | Daihatsu | Grand Move | 33.8% | 15,943 |
| 10 | Vauxhall | Vectra Ls 16v | 33.3% | 9,873 |
| 11 | Rover | 214 | 33.3% | 250,006 |
| 12 | Fiat | Brava | 33.1% | 110,514 |
| 13 | Mitsubishi | Fto | 32.6% | 21,648 |
| 14 | Daewoo | Nexia | 32.2% | 11,733 |
| 15 | Audi | A4 1.8 | 32.2% | 11,368 |
| 16 | Mazda | Mx6 | 32% | 8,129 |
| 17 | Mitsubishi | Space Wagon | 30.4% | 50,856 |
| 18 | Toyota | Carina E | 29.5% | 133,790 |
| 19 | Rover | 200 | 29.1% | 20,251 |
| 20 | Citroen | Ax | 28.2% | 67,595 |
💡 How to Avoid Noise, emissions and leaks Failures
- ✓ Take your car for a 20-minute motorway drive before the MOT to get the catalytic converter up to temperature — this helps pass emissions.
- ✓ Fix exhaust leaks and replace damaged sections — a hole in the exhaust will fail on both noise and emissions.
- ✓ Use the correct engine oil grade and keep the engine well-serviced. Old spark plugs and dirty air filters increase emissions.
Frequently Asked Questions
How can I reduce my car's emissions before an MOT?
Drive at motorway speed for 20+ minutes before the test to heat the catalytic converter. Ensure the engine is serviced with fresh oil, clean air filter, and good spark plugs. For diesels, a DPF regeneration drive helps clear soot.
Do electric cars get tested for emissions?
No — fully electric vehicles are exempt from emissions testing in the MOT. Hybrid vehicles are tested on their combustion engine emissions only.
What emission limits apply in the MOT?
Petrol cars registered after 2002 must meet strict catalyst-era limits. Diesel cars are tested for smoke opacity. Limits vary by registration date, with newer cars having tighter requirements.
Based on DVSA anonymised MOT test data (2005–2024). Crown copyright, Open Government Licence v3.0.