(2021 registrations)
2021 cohort
at first test
after a failure
The A3 was Britain’s ninth best-selling new car in 2023 with 30,159 registrations, and the 8Y generation that arrived in 2020 is a genuinely well-built compact premium car. A 2021 example posts the highest pass rate of any A3 registration year on record. Almost all of its expensive failures trace back to one component and one service item — the S tronic dual-clutch gearbox, and the fluid change that most owners never book.
Figures are derived from the DVSA anonymised MOT tests and results dataset, published under the Open Government Licence v3.0. Every MOT records the test outcome plus each defect as a coded “reason for rejection” or advisory.
Percentages are share of tests, not share of failures — so “2.6% tyre tread” means 2.6 in every 100 tests failed for that item. A single test can record several defects, so the columns do not sum to 100%.
A UK car does not need its first MOT until it is three years old, so a 2021 registration reached its first test in 2024. Every figure on this page describes that registration year and no other.
The 2021 cohort covers only 428 tests at an average of 26,804 miles, so read the figure as encouraging rather than settled.
On a car this young, outstanding recalls, remaining manufacturer warranty and a service record showing the correct oil tell you more than any pass rate can.
Top MOT failure items
These are the defects that actually caused a Audi A3 (2021) to fail its MOT, ranked by how often they appear across all tests.
Most common MOT advisories
Advisories are the early-warning layer. They don’t fail the car, but they tell you what the next owner will be paying for — and they are the single most useful thing to read before you buy.
| Advisory item | Share of tests | What it means |
|---|---|---|
| Tyre worn close to legal limit | 11.4% | Larger alloys make this a bigger bill than on a mainstream hatch. |
| Suspension joint dust cover deteriorated | 9.8% | The precursor to the No.2 failure item — cheap now, a joint later. |
| Brake pads wearing thin | 8.6% | Budget £180–£320 per axle at an independent. |
| Brake disc lipped or scored | 5.3% | Usually replaced with pads. |
| Suspension bush deteriorated | 4.7% | Firm suspension is hard on bushes. |
| Coil spring corroded | 3.1% | Directly ahead of the No.3 failure item. |
| Engine oil leak (not excessive) | 2.4% | Worth investigating on an 8Y. |
| Brake fluid contaminated | 2.0% | Due around the first and third tests. |
| Wiper blade deteriorated | 1.9% | Cheap, but a failure if it smears. |
| Exhaust minor corrosion | 1.5% | Surface only at this age. |
Which system fails most
Grouping every recorded defect by vehicle system shows where the money goes on a three-year-old A3.
The 2021 registration year passes at 93.5%, the highest of any A3 year in the data, at an average of 26,804 miles — but across only 428 tests, because these cars were only just reaching their first MOT. Across all generations the A3 passes at 80.5% over 632,300 tests, at a median 98,621 miles, with an average repair bill after a failure of £111.
The fuel split is wide and worth acting on: petrol A3s pass at 83.7% across 325,042 tests, diesel at 77.1% across 303,343, and the smaller hybrid sample at 87.9%. The all-generation average is dragged down by a dataset reaching back to 1997 — a 1998 A3 passes at 66.8%. On a 2021 car the service record is the evidence that matters, not the headline pass rate.
Model averages describe the model. Enter the registration to see this car’s real MOT history, every recorded advisory, its mileage timeline and any finance, theft or write-off markers.
The S tronic question, and the service nobody books
The 8Y A3 does not have a signature catastrophic fault in the way some cars on this site do. What it has is a gearbox that is fine when maintained and expensive when it is not — and a maintenance item that is easy to skip because nothing warns you.
- Symptoms build gradually: rough or jerky shifts, hesitation, clutch judder from a standstill, and eventually an EPC warning or a refusal to engage a gear.
- The aluminium mechatronic housing can develop micro-cracks around the pressure accumulator from repeated heat and pressure cycling.
- This is the one genuinely expensive failure on the car, and it is far more common on examples with no record of a gearbox fluid change.
- Test it in a car park and in traffic, not just on a main road — low-speed manoeuvring is where judder shows.
- S tronic gearboxes depend on clean, uncontaminated fluid. The recommended oil and filter interval is around 40,000 miles.
- It is the most commonly skipped service item on these cars, because nothing on the dashboard asks for it.
- Ask for the invoice by name. A car with a documented gearbox oil and filter change at the right mileage is a materially different purchase from one without.
- A manual, where you can find one, removes the question entirely — and the 1.5 TFSI petrol is the best-balanced engine in the range.
Known faults the MOT won’t catch
The MOT tests roadworthiness, not mechanical health. These are the expensive items owners actually report — costs are indicative UK independent-specialist ranges, not quotes.
Pre-purchase checklist
Work through this in order. The first few cost nothing and rule out most bad cars.
- Ask for the S tronic oil and filter invoice specifically. It is not part of a normal service and is the single most useful document on this car.
- Drive it in a car park and in traffic, not just on a main road. Judder from a standstill is what you are listening for.
- Start it from cold and listen for chain rattle in the first few seconds.
- Confirm both recalls that reach a 2021 car — the fuse carrier connector (built March 2020 to May 2023) and the brake servo to pedal connection (built August 2020 to May 2021).
- Check outstanding recalls by registration on the DVSA service. The work is free.
- Prefer petrol unless you genuinely need diesel mileage. Across the model, petrol passes 6.6 points ahead of diesel.
- Look underneath at the springs and joint dust covers — the No.2 and No.3 failure items on this model.
- Verify finance and write-off status. Premium compact cars are heavily financed and a three-year-old A3 is a typical PCP return.
FAQs
Is the Audi A3 reliable?
The 8Y generation is solid: 2020 registrations pass the MOT at 91.4% and 2021 cars at 93.5%, well above the UK average, with a modest £111 average repair bill across the model. The exception is the S tronic gearbox, which is reliable when its fluid is changed and expensive when it is not.
What is the Audi S tronic 40,000-mile service?
An oil and filter change for the dual-clutch gearbox. It is not included in a standard interim or major service and nothing on the dashboard prompts it, so it is routinely skipped. Clean fluid is what prevents the clutch and mechatronic faults that make up the car’s most expensive repairs.
Should I buy a petrol or diesel A3?
Petrol, unless you cover very high mileage. Across 632,300 MOT tests, petrol A3s pass at 83.7% and diesels at 77.1% — a 6.6 point gap. The 1.5 TFSI is generally considered the best-balanced engine in the range.
What recalls affect the 2021 Audi A3?
A 2021 car can fall inside three. The fuse carrier connector recall covers builds from March 2020 to May 2023. The brake servo to pedal connection recall covers August 2020 to May 2021 and is the most serious of them, because a loosening connection risks losing braking. On plug-in hybrids, a high-voltage fuse recall covers October 2020 to February 2022. All three are free to rectify — check by registration.
Why is the headline A3 pass rate only 80.5%?
Because the dataset reaches back to 1997 and includes every generation. A 1998 A3 passes at 66.8%. The current 8Y cars pass in the low 90s, which is the figure that describes a 2021 car.
A CarCheckReport covers MOT and advisory history, mileage anomalies, outstanding finance, insurance write-off records, stolen markers, import and scrapped status — using DVLA, DVSA and Experian data.