BMW 3 Series or Audi A4? It's the most-asked question in the Irish premium used-car market. Both are excellent cars — but they have meaningfully different strengths, fault profiles, and running costs at different budgets and mileage points. This comparison is written for Irish buyers looking at 2016–2022 used examples.
The short answer
For outright driving enjoyment, the BMW 3 Series wins. For interior quality and technology, the Audi A4 edges ahead. For practical space, the Audi A4 Avant estate beats the BMW 3 Series Touring for boot volume (505 vs 495 litres). For running costs, both are broadly similar when serviced at a brand specialist — but the BMW has a more serious engine-specific risk (N47 diesel timing chain failure) than the A4 on comparable years. If you're buying a pre-2016 diesel, the A4 TDI is the lower-risk choice; for petrols, the BMW 320i/330i is excellent.
Engines: which to choose
The diesels
Both the BMW 320d (N47 pre-2015, B47 post-2015) and the Audi A4 2.0 TDI are popular in Ireland and offer excellent fuel economy on motorway routes (typically 5.0–5.5 L/100km). The critical difference:
- BMW N47 diesel (2012–2015): Rear-mounted timing chain. Known to fail from 100,000 km, requiring engine removal — a €3,000–€6,000 repair. Check chain history.
- BMW B47 diesel (2015+): Revised engine, no inherited chain problem. The B47 is significantly more reliable.
- Audi 2.0 TDI (B9): Timing belt, not chain. Belt must be changed every 90,000–130,000 km (Audi says 130k; many specialists recommend 90k for Irish use). Belt failure = engine write-off. Check belt history.
Both have a serious diesel maintenance requirement — but the BMW N47 fails more suddenly (chain snaps without warning) while the Audi TDI gives you a scheduled service point to work from. A post-2015 BMW 320d (B47) with verified service history is arguably the safer diesel buy.
The petrols
- BMW 320i/330i (B46/B48, 2015+): Excellent engines — smooth, powerful, and well-proven. The B48 in the G20 3 Series (2019+) is one of the best 4-cylinder petrols in the segment. Known issue: electric water pump from 80,000 km.
- Audi A4 35 TFSI MHEV (2019+): Mild hybrid system, competitive fuel economy, Chain-driven (no belt risk). The MHEV 35 TFSI is the most trouble-free petrol in the A4 B9 range.
Automatic gearboxes: a shared concern
Both the BMW ZF 8-speed automatic and the Audi S-Tronic DSG are excellent gearboxes — smooth, fast, and well-suited to Irish road conditions. But both require a fluid service every 60,000 km, and both develop judder or fault codes above 100,000 km without this service. Ask for gearbox service history on any automatic example of either car.
Interior quality: Audi wins
The Audi A4 B9 interior is widely considered the most refined in the D-segment. The materials quality, fit and finish, and the Virtual Cockpit digital instrument cluster are excellent. The BMW F30/G20 interior is very good but one step below the A4 for perceived luxury — the F30 (2012–2019) in particular feels less special than the G20 (2019+). If interior quality is a priority and budget allows a 2019+ G20, it closes the gap significantly.
Driving dynamics: BMW wins
The BMW 3 Series has one of the best driving dynamics of any car in its class — rear-wheel drive (or sophisticated xDrive AWD), near-50/50 weight distribution, and a chassis tuned for driver involvement. The Audi A4 is a very competent driver's car but uses front-wheel drive (or Quattro AWD) and prioritises comfort and stability over outright driver engagement. If you enjoy driving, the BMW is more rewarding.
Practicality: Avant vs Touring estate
Both are available as estates — the BMW 3 Series Touring and the Audi A4 Avant. The Audi A4 Avant boot (505 litres, seats up) is slightly larger than the BMW 3 Series Touring (495 litres). Both have fold-flat rear seats. Both have standard-spec roof rails on Avant/Touring variants. For family estate use, the practical difference is marginal — it comes down to which brand and model you prefer.
Running costs comparison
| Item | BMW 3 Series | Audi A4 |
|---|---|---|
| Service interval | 15,000 km / 12 months | 15,000 km / 12 months (not longlife) |
| Oil service (specialist) | €180–€280 | €200–€300 |
| Timing chain (BMW N47) | €3,000–€6,000 (if needed) | N/A (petrol) / belt service €700–€1,200 (diesel) |
| DSG/ZF gearbox service | €300–€500 (ZF 8HP) | €400–€700 (S-Tronic) |
| Typical front brake service | €350–€600 | €400–€650 |
| Motor tax (320d / 2.0 TDI) | €200–€270/year | €200–€270/year |
| Insurance (Group) | 20–32 | 22–32 |
Which years to buy (used Irish market, 2026)
BMW 3 Series
- Best buy: G20 2019+ — B47/B48 engines, no inherited chain issues, best interior
- Good buy: F30 2016–2019 facelift with B47 diesel or B48 petrol, verified service history
- Be careful: F30 2012–2015 with N47 diesel — check chain history carefully; walk away if unverified above 120,000 km
Audi A4
- Best buy: B9 facelift 2019+ with 35 TFSI MHEV petrol or 40 TDI diesel, full service history
- Good buy: B9 2016–2019 with 2.0 TDI — verify timing belt change at 90,000 km or 4 years
- Be careful: Any 2.0 TDI without documented belt change at the correct interval — belt failure is catastrophic
The Autoza verdict
Both are excellent cars. Buy the BMW 3 Series if you prioritise driving enjoyment and are targeting a post-2015 B47 diesel or B48 petrol G20. Buy the Audi A4 if you prioritise interior quality, technology, and the Avant estate body for family use — and verify the TDI timing belt history without exception.
Both require specialist maintenance to keep running costs manageable. Neither is the right choice if budget-of-ownership is the primary concern — a Skoda Octavia diesel estate offers 80% of the capability at significantly lower cost.
Further reading
Autoza has detailed year-by-year fault guides for both: BMW 3 Series common faults guide and Audi A4 common faults guide.
