2021 Audi A4 S Line 35 Mhev S-A — MOT failures & pass rate
Across 3,231 MOT tests analysed for the 2021 Audi A4 S Line 35 Mhev S-A, the most common recorded failure areas were tyres, lighting & signalling and visibility. Its pass rate of 89.6% was below the average for cars of a similar age (91.2%). Higher-mileage examples failed more often — 14.5% in the 90-120k group versus 8.4% in the 0-30k group.
How it compares
Top failure categories
| # | Category | % of tests affected | Tests |
|---|---|---|---|
| 1 | Tyres | 7.5% | 241 |
| 2 | Lighting & signalling | 1.4% | 45 |
| 3 | Visibility | 1.2% | 38 |
| 4 | Brakes | 1.1% | 34 |
| 5 | Emissions & environmental | 0.7% | 24 |
| 6 | Suspension | 0.5% | 17 |
Most common specific failures
The exact components most often recorded as failures — more specific than the categories above.
| # | Failure item | Times recorded |
|---|---|---|
| 1 | Tread depth | 95 |
| 2 | Headlamp aim | 51 |
| 3 | Wipers | 31 |
| 4 | Brake pads | 30 |
| 5 | Malfunction indicator lamp | 23 |
| 6 | Washers | 14 |
Top advisory categories
Advisories aren't failures, but they flag work likely needed soon — useful when budgeting.
| # | Category | % of tests with advisory | Tests |
|---|---|---|---|
| 1 | Tyres | 25.4% | 819 |
| 2 | Brakes | 11.2% | 362 |
| 3 | Other defects | 8.0% | 258 |
| 4 | Suspension | 3.9% | 127 |
| 5 | Visibility | 3.3% | 107 |
| 6 | Road wheels | 1.0% | 31 |
Failure rate by mileage
Higher-mileage cars tend to fail more — often the most useful guide to real condition.
| Mileage band | Tests | Fail rate |
|---|---|---|
| 0-30k | 860 | 8.4% |
| 30-60k | 1,940 | 11.2% |
| 60-90k | 347 | 10.1% |
| 90-120k | 69 | 14.5% |
Failure rate by age
By fuel type
| Fuel | Tests | Fail rate |
|---|---|---|
| Diesel | 2,570 | 10.3% |
| Petrol | 652 | 10.7% |
Trend over time
| Dataset year | Tests | Fail rate |
|---|---|---|
| 2023 | 67 | 11.9% |
| 2024 | 1,650 | 10.4% |
| 2025 | 1,514 | 10.2% |
What to check before buying a 2021 A4 S Line 35 Mhev S-A
Before buying a 2021 Audi A4 S Line 35 Mhev S-A, focus on the areas it most often fails on. Tyres accounted for 7.5% of tests for this year.
- Tyres (7.5% of tests): Usually a quick, known-cost fix, but check tread, age and uneven wear (which can hint at alignment or suspension issues). Typical repair: £50–£120 per tyre.
- Lighting & signalling (1.4% of tests): Often a cheap bulb, but persistent issues can mean wiring or corrosion in the units. Typical repair: £10–£150.
- Visibility (1.2% of tests): Wipers, washers, mirrors and screen damage — usually inexpensive, but check for chips in the driver's line of sight. Typical repair: £15–£150.
Repair costs are rough UK ballpark ranges to set expectations, not quotes — actual prices vary widely by car, parts and garage.
Frequently asked questions
How many 2021 Audi A4 S Line 35 Mhev S-As pass their MOT?
89.6% of the 3,231 2021 Audi A4 S Line 35 Mhev S-A MOT tests in this dataset passed — a 10.4% fail rate.
What is the most common MOT failure on a 2021 Audi A4 S Line 35 Mhev S-A?
Tyres, recorded in 7.5% of tests, followed by lighting & signalling (1.4%).
Does the 2021 A4 S Line 35 Mhev S-A get worse with mileage?
Its MOT fail rate rises from 8.4% in the 0-30k band to 14.5% in the 90-120k band.
Methodology & source. Based on 3,231 MOT tests. Dataset: DVSA MOT testing data (2021,2022,2023,2024,2025). Data last updated 2026-07-01. Figures reflect MOT-testable defects only — read the methodology for how these are calculated and what they don't measure.